added migrated 2.x add-ons

Signed-off-by: Kai Kreuzer <kai@openhab.org>

bundles/org.openhab.binding.modbus/.classpath

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" output="target/classes" path="src/main/java">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry excluding="**" kind="src" output="target/classes" path="src/main/resources">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" output="target/test-classes" path="src/test/java">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="test" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-11">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="output" path="target/classes"/>
+</classpath>

bundles/org.openhab.binding.modbus/.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>org.openhab.binding.modbus</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.m2e.core.maven2Builder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+		<nature>org.eclipse.m2e.core.maven2Nature</nature>
+	</natures>
+</projectDescription>

bundles/org.openhab.binding.modbus/DEVELOPERS.md

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+# For Developers
+
+## Debugging an addon
+
+Please follow IDE setup guide at https://www.openhab.org/docs/developer/ide/eclipse.html.
+
+When configuring dependencies in `openhab-distro/launch/app/pom.xml`, add all dependencies, including the transitive dependencies:
+
+```xml
+<dependency>
+    <groupId>org.openhab.addons.bundles</groupId>
+    <artifactId>org.openhab.binding.modbus</artifactId>
+    <version>${project.version}</version>
+    <scope>runtime</scope>
+</dependency>
+<dependency>
+    <groupId>org.openhab.addons.bundles</groupId>
+    <artifactId>org.openhab.io.transport.modbus</artifactId>
+    <version>${project.version}</version>
+    <scope>runtime</scope>
+</dependency>
+<dependency>
+    <groupId>org.openhab.osgiify</groupId>
+    <artifactId>net.wimpi.jamod</artifactId>
+    <version>1.2.4.OH</version>
+    <scope>runtime</scope>
+</dependency>
+```
+
+## Testing Serial Implementation
+
+You can use test serial slaves without any hardware on Linux using these steps:
+
+1. Set-up virtual null modem emulator using [tty0tty](https://github.com/freemed/tty0tty)
+2. Download [diagslave](https://www.modbusdriver.com/diagslave.html) and start modbus serial slave up using this command:
+
+```
+./diagslave -m rtu -a 1 -b 38400 -d 8 -s 1 -p none -4 10 /dev/pts/7
+```
+
+3. Configure openHAB's modbus slave to connect to `/dev/pts/8`.
+
+4. Modify `start.sh` or `start_debug.sh` to include the unconventional port name by adding the following argument to `java`:
+
+```
+-Dgnu.io.rxtx.SerialPorts=/dev/pts/8
+```
+
+Naturally this is not the same thing as the real thing but helps to identify simple issues.
+
+## Testing TCP Implementation
+
+1. Download [diagslave](https://www.modbusdriver.com/diagslave.html) and start modbus tcp server (slave) using this command:
+
+```
+./diagslave -m tcp -a 1 -p 55502
+```
+
+2. Configure openHAB's modbus slave to connect to `127.0.0.1:55502`.
+
+
+## Writing Data
+
+See this [community post](https://community.openhab.org/t/something-is-rounding-my-float-values-in-sitemap/13704/32?u=ssalonen) explaining how `pollmb` and `diagslave` can be used to debug modbus communication.
+
+You can also use `modpoll` to write data:
+
+
+```bash
+# write value=5 to holding register 40001 (index=0 in the binding)
+./modpoll -m tcp -a 1 -r 1 -t4 -p 502 127.0.0.1 5
+# set coil 00001 (index=0 in the binding) to TRUE
+./modpoll -m tcp -a 1 -r 1 -t0 -p 502 127.0.0.1 1
+# write float32
+./modpoll -m tcp -a 1 -r 1 -t4:float -p 502 127.0.0.1 3.14
+```
+
+## Extending Modbus binding
+
+This Modbus binding can be extended by other OSGi bundles to add more specific support for Modbus enabled devices.
+To do so to you have to create a new OSGi bundle which has the same binding id as this binding.
+The best way is to use the `ModbusBindingConstants.BINDING_ID` constant.
+
+You will have to create one or more handler classes for the devices you want to support.
+For the modbus connection setup and handling you can use the Modbus TCP Slave or Modbus Serial Slave handlers.
+Your handler should use these handlers as bridges and you can set up your regular or one shot modbus requests to read from the slave.
+This is done by by creating a `BasicPollTaskImpl` and submitting it using the `ModbusManager` `submitOneTimePoll` and `registerRegularPoll` methods.
+
+Please keep in mind that these reads are asynchronous and they will call your callback once the read is done.
+
+Once you have your data read from the modbus device you can parse and transform them then update your channels to publish these data to the openHAB system.
+
+### Discovery
+
+If you write a device specific handler then adding discovery for this device is very welcome.
+You will have to write a discovery participant class which implements the `ModbusDiscoveryParticipant` interface and registers itself as a component. Example:
+
+```java
+
+@Component(immediate = true)
+@NonNullByDefault
+public class SunspecDiscoveryParticipant implements ModbusDiscoveryParticipant {
+...
+}
+```
+
+There are two methods you have to implement:
+
+ - `getSupportedThingTypeUIDs` should return a list of the thing type UIDs that are supported by this discovery participant. This is fairly straightforward.
+ 
+ - `startDiscovery` method will be called when a discovery process has began. This method receives two parameters:
+ 
+    - `ModbusEndpointThingHandler` is the endpoint's handler that should be tested if it is known by your bundle. You can start your read requests against this handler.
+    
+    - `ModbusDiscoveryListener` this listener instance should be used to report any known devices found and to notify the main discovery process when your binding has finished the discovery.
+    
+Please try to avoid write requests to the endpoint because it could be some unknown device that write requests could misconfigure.
+
+When a known device is found a `DiscoveryResult` object has to be created then the `thingDiscovered` method has to be called.
+The `DiscoveryResult` supports properties, and you should use this to store any data that will be useful when the actual thing will be created.
+For example you could store the start Modbus address of the device or vendor/model informations.
+
+When the discovery process is finished either by detecting a device or by realizing it is not supported you should call the `discoveryFinished` method.
+This will tear down any resources allocated for the discovery process.
+
+
+### Discovery Architecture
+
+The following diagram shows the concept how discovery is implemented in this binding. (Note that some intermediate classes and interfaces are not shown for clarity.)
+
+![Discovery architecture](doc/images/ModbusExtensibleDiscovery.png)
+
+As stated above the discovery process can be extended by OSGi bundles.
+For this they have to define their own `ModbusDisvoceryParticipant` that gets registered at the `ModbusDiscoveryService`.
+This object also keeps track of any of the Modbus handlers.
+Handler level discovery logic is implemented in the `ModbusEndpointDiscoveryService` which gets instantiated for each Modbus `BridgeHandler`.
+
+The communication flow is detailed in the diagram below:
+
+![Discovery process](doc/images/DiscoveryProcess.png)
+
+As can be seen the process is initiated by the `ModbusDiscoveryService` which calls each of the `ModbusEndpointDiscoveryService` instances to start the discovery on the available participants.
+Then a reference to the `ThingHandler` is passed to each of the participants who can use this to do the actual discovery.
+
+Any things discovered are reported back in this chain and ultimately sent to openHAB core.

bundles/org.openhab.binding.modbus/NOTICE

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+This content is produced and maintained by the openHAB project.
+
+* Project home: https://www.openhab.org
+
+== Declared Project Licenses
+
+This program and the accompanying materials are made available under the terms
+of the Eclipse Public License 2.0 which is available at
+https://www.eclipse.org/legal/epl-2.0/.
+
+== Source Code
+
+https://github.com/openhab/openhab-addons

bundles/org.openhab.binding.modbus/pom.xml

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+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>org.openhab.addons.bundles</groupId>
+    <artifactId>org.openhab.addons.reactor.bundles</artifactId>
+    <version>3.0.0-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>org.openhab.binding.modbus</artifactId>
+
+  <name>openHAB Add-ons :: Bundles :: Modbus Binding</name>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.openhab.addons.bundles</groupId>
+      <artifactId>org.openhab.io.transport.modbus</artifactId>
+      <version>${project.version}</version>
+      <scope>provided</scope>
+    </dependency>
+  </dependencies>
+
+</project>

bundles/org.openhab.binding.modbus/src/main/feature/feature.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<features name="org.openhab.binding.modbus-${project.version}" xmlns="http://karaf.apache.org/xmlns/features/v1.4.0">
+	<repository>file:${basedirRoot}/bundles/org.openhab.io.transport.modbus/target/feature/feature.xml</repository>
+
+	<feature name="openhab-binding-modbus" description="Modbus Binding" version="${project.version}">
+		<feature>openhab-runtime-base</feature>
+		<feature>openhab-transport-modbus</feature>
+		<bundle start-level="80">mvn:org.openhab.addons.bundles/org.openhab.binding.modbus/${project.version}</bundle>
+	</feature>
+</features>

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/ModbusBindingConstants.java

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+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+
+/**
+ * The {@link ModbusBinding} class defines some constants
+ * public that might be used from other bundles as well.
+ *
+ * @author Sami Salonen - Initial contribution
+ * @author Nagy Attila Gabor - Split the original ModbusBindingConstants in two
+ */
+@NonNullByDefault
+public class ModbusBindingConstants {
+
+    public static final String BINDING_ID = "modbus";
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/discovery/ModbusDiscoveryListener.java

@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.discovery;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.core.config.discovery.DiscoveryResult;
+
+/**
+ * Listener for discovery results
+ *
+ * Each discovered thing should be supplied to the thingDiscovered
+ * method.
+ *
+ * When the discovery process has been finished then the discoveryFinished
+ * method should be called.
+ *
+ * @author Nagy Attila Gabor - initial contribution
+ *
+ */
+@NonNullByDefault
+public interface ModbusDiscoveryListener {
+
+    /**
+     * Discovery participant should call this method when a new
+     * thing has been discovered
+     */
+    public void thingDiscovered(DiscoveryResult result);
+
+    /**
+     * This method should be called once the discovery has been finished
+     * or aborted by any error.
+     * It is important to call this even when there were no things discovered.
+     */
+    public void discoveryFinished();
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/discovery/ModbusDiscoveryParticipant.java

@@ -0,0 +1,48 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.discovery;
+
+import java.util.Set;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.binding.modbus.handler.ModbusEndpointThingHandler;
+import org.openhab.core.thing.ThingTypeUID;
+
+/**
+ * Interface for participants of Modbus discovery
+ * This is an asynchronous process where a participant can discover
+ * multiple things on a Modbus endpoint.
+ *
+ * Results should be submitted using the ModbusDiscvoeryListener
+ * supplied at the begin of the scan.
+ *
+ * @author Nagy Attila Gabor - initial contribution
+ *
+ */
+@NonNullByDefault
+public interface ModbusDiscoveryParticipant {
+
+    /**
+     * Defines the list of thing types that this participant can identify
+     *
+     * @return a set of thing type UIDs for which results can be created
+     */
+    public Set<ThingTypeUID> getSupportedThingTypeUIDs();
+
+    /**
+     * Start an asynchronous discovery process of a Modbus endpoint
+     *
+     * @param handler the endpoint that should be discovered
+     */
+    public void startDiscovery(ModbusEndpointThingHandler handler, ModbusDiscoveryListener listener);
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/discovery/internal/ModbusDiscoveryService.java

@@ -0,0 +1,188 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.discovery.internal;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.binding.modbus.discovery.ModbusDiscoveryParticipant;
+import org.openhab.core.config.discovery.AbstractDiscoveryService;
+import org.openhab.core.config.discovery.DiscoveryResult;
+import org.openhab.core.config.discovery.DiscoveryService;
+import org.openhab.core.thing.ThingTypeUID;
+import org.osgi.service.component.annotations.Component;
+import org.osgi.service.component.annotations.Reference;
+import org.osgi.service.component.annotations.ReferenceCardinality;
+import org.osgi.service.component.annotations.ReferencePolicy;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ *
+ * Discovery service for Modbus bridges.
+ *
+ * This service acts as a rendezvous point between the different Modbus endpoints and any
+ * bundles that implement auto discovery through an endpoint.
+ *
+ * New bridges (TCP or Serial Modbus endpoint) should register with this service. This is
+ * handled automatically by the ModbusEndpointDiscoveryService.
+ * Also any bundles that perform auto discovery should register a ModbusDiscoveryParticipant.
+ * This ModbusDiscoveryParticipants will be called by the service when
+ * a discovery scan is requested.
+ *
+ * @author Nagy Attila Gabor - initial contribution
+ *
+ */
+@Component(immediate = true, service = DiscoveryService.class, configurationPid = "discovery.modbus")
+@NonNullByDefault
+public class ModbusDiscoveryService extends AbstractDiscoveryService {
+
+    private final Logger logger = LoggerFactory.getLogger(ModbusDiscoveryService.class);
+
+    // Set of services that support Modbus discovery
+    private final Set<ModbusThingHandlerDiscoveryService> services = new CopyOnWriteArraySet<>();
+
+    // Set of the registered participants
+    private final Set<ModbusDiscoveryParticipant> participants = new CopyOnWriteArraySet<>();
+
+    // Set of the supported thing types. This is a union of all the thing types
+    // supported by the registered discovery services.
+    private final Set<ThingTypeUID> supportedThingTypes = new CopyOnWriteArraySet<>();
+
+    private static final int SEARCH_TIME_SECS = 5;
+
+    /**
+     * Constructor for the discovery service.
+     * Set up default parameters
+     */
+    public ModbusDiscoveryService() {
+        // No supported thing types by default
+        // Search time is for the visual reference
+        // Background discovery disabled by default
+        super(null, SEARCH_TIME_SECS, false);
+    }
+
+    /**
+     * ThingHandlerService
+     * Begin a discovery scan over each endpoint
+     */
+    @Override
+    protected void startScan() {
+        logger.trace("ModbusDiscoveryService starting scan");
+
+        if (participants.isEmpty()) {
+            // There's no point on continuing if there are no participants at the moment
+            stopScan();
+            return;
+        }
+
+        boolean scanStarted = false;
+        for (ModbusThingHandlerDiscoveryService service : services) {
+            scanStarted |= service.startScan(this);
+        }
+        if (!scanStarted) {
+            stopScan();
+        }
+    }
+
+    /**
+     * Interface to notify us when a handler has finished it's discovery process
+     */
+    protected void scanFinished() {
+        for (ModbusThingHandlerDiscoveryService service : services) {
+            if (service.scanInProgress()) {
+                return;
+            }
+        }
+        logger.trace("All endpoints finished scanning, stopping scan");
+        stopScan();
+    }
+
+    /**
+     * Real discovery is done by the ModbusDiscoveryParticipants
+     * They are executed in series for each Modbus endpoint by ModbusDiscoveryProcess
+     * instances. They call back this method when a thing has been discovered
+     */
+    @Override
+    protected void thingDiscovered(DiscoveryResult discoveryResult) {
+        super.thingDiscovered(discoveryResult);
+    }
+
+    /**
+     * Returns the list of {@code Thing} types which are supported by the {@link DiscoveryService}.
+     *
+     * @return the list of Thing types which are supported by the discovery service
+     *         (not null, could be empty)
+     */
+    @Override
+    public Set<ThingTypeUID> getSupportedThingTypes() {
+        return this.supportedThingTypes;
+    }
+
+    /**
+     * This reference is used to register any new Modbus bridge with the discovery service
+     * Running bridges have a ModbusThingHandlerDiscoveryService connected
+     * which will be responsible for the discovery
+     *
+     * @param handler the Modbus bridge handler
+     */
+    @Reference(cardinality = ReferenceCardinality.MULTIPLE, policy = ReferencePolicy.DYNAMIC)
+    protected void addModbusEndpoint(ModbusThingHandlerDiscoveryService service) {
+        logger.trace("Received new handler: {}", service);
+        services.add(service);
+    }
+
+    /**
+     * Remove an already registered thing handler discovery component
+     *
+     * @param handler the handler that has been removed
+     */
+    protected void removeModbusEndpoint(ModbusThingHandlerDiscoveryService service) {
+        logger.trace("Removed handler: {}", service);
+        services.remove(service);
+    }
+
+    /**
+     * Register a discovery participant. This participant will be called
+     * with any new Modbus bridges that allow discovery
+     *
+     * @param participant
+     */
+    @Reference(cardinality = ReferenceCardinality.MULTIPLE, policy = ReferencePolicy.DYNAMIC)
+    protected void addModbusDiscoveryParticipant(ModbusDiscoveryParticipant participant) {
+        logger.trace("Received new participant: {}", participant);
+        participants.add(participant);
+        supportedThingTypes.addAll(participant.getSupportedThingTypeUIDs());
+    }
+
+    /**
+     * Remove an already registered discovery participant
+     *
+     * @param participant
+     */
+    protected void removeModbusDiscoveryParticipant(ModbusDiscoveryParticipant participant) {
+        logger.trace("Removing participant: {}", participant);
+        supportedThingTypes.removeAll(participant.getSupportedThingTypeUIDs());
+        participants.remove(participant);
+    }
+
+    /**
+     * Return the set of participants
+     *
+     * @return a set of the participants. Note: this is a copy of the original set
+     */
+    public Set<ModbusDiscoveryParticipant> getDiscoveryParticipants() {
+        return new CopyOnWriteArraySet<>(participants);
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/discovery/internal/ModbusEndpointDiscoveryService.java

@@ -0,0 +1,126 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.discovery.internal;
+
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+import org.openhab.binding.modbus.discovery.ModbusDiscoveryListener;
+import org.openhab.binding.modbus.discovery.ModbusDiscoveryParticipant;
+import org.openhab.binding.modbus.handler.ModbusEndpointThingHandler;
+import org.openhab.core.config.discovery.DiscoveryResult;
+import org.openhab.core.thing.binding.ThingHandler;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * A new instance of this class is created for each Modbus endpoint handler
+ * that supports discovery.
+ * This service gets called each time a discovery is requested, and it is
+ * responsible to execute the discovery on the connected thing handler.
+ * Actual discovery is done by the registered ModbusDiscoveryparticipants
+ *
+ * @author Nagy Attila Gabor - initial contribution
+ *
+ */
+@NonNullByDefault
+public class ModbusEndpointDiscoveryService implements ModbusThingHandlerDiscoveryService {
+
+    private final Logger logger = LoggerFactory.getLogger(ModbusEndpointDiscoveryService.class);
+
+    // This is the handler we will do the discovery on
+    private @Nullable ModbusEndpointThingHandler handler;
+
+    // List of the registered participants
+    // this only contains data when there is scan in progress
+    private final List<ModbusDiscoveryParticipant> participants = new CopyOnWriteArrayList<>();
+
+    // This is set true when we're waiting for a participant to finish discovery
+    private boolean waitingForParticipant = false;
+
+    @Override
+    public void setThingHandler(@Nullable ThingHandler handler) {
+        if (handler instanceof ModbusEndpointThingHandler) {
+            this.handler = (ModbusEndpointThingHandler) handler;
+        }
+    }
+
+    @Override
+    public @Nullable ThingHandler getThingHandler() {
+        return (ThingHandler) handler;
+    }
+
+    @Override
+    public boolean startScan(ModbusDiscoveryService service) {
+        ModbusEndpointThingHandler handler = this.handler;
+        if (handler == null || !handler.isDiscoveryEnabled()) {
+            return false;
+        }
+        logger.trace("Starting discovery on endpoint {}", handler.getUID().getAsString());
+
+        participants.addAll(service.getDiscoveryParticipants());
+
+        startNextParticipant(handler, service);
+
+        return true;
+    }
+
+    @Override
+    public boolean scanInProgress() {
+        return !participants.isEmpty() || waitingForParticipant;
+    }
+
+    /**
+     * Run the next participant's discovery process
+     *
+     * @param service reference to the ModbusDiscoveryService that will collect all the
+     *            discovered items
+     */
+    private void startNextParticipant(final ModbusEndpointThingHandler handler, final ModbusDiscoveryService service) {
+        if (participants.isEmpty()) {
+            logger.trace("All participants has finished");
+            service.scanFinished();
+            return; // We're finished, this will exit the process
+        }
+
+        ModbusDiscoveryParticipant participant = participants.remove(0);
+
+        waitingForParticipant = true;
+
+        // Call startDiscovery on the next participant. The ModbusDiscoveryListener
+        // callback will be notified each time a thing is discovered, and also when
+        // the discovery is finished by this participant
+        participant.startDiscovery(handler, new ModbusDiscoveryListener() {
+
+            /**
+             * Participant has found a thing
+             */
+            @Override
+            public void thingDiscovered(DiscoveryResult result) {
+                service.thingDiscovered(result);
+            }
+
+            /**
+             * Participant finished discovery.
+             * We can continue to the next participant
+             */
+            @Override
+            public void discoveryFinished() {
+                waitingForParticipant = false;
+                startNextParticipant(handler, service);
+            }
+        });
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/discovery/internal/ModbusThingHandlerDiscoveryService.java

@@ -0,0 +1,43 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.discovery.internal;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.core.thing.binding.ThingHandlerService;
+
+/**
+ * Implementation of this interface is responsible for discovery over
+ * a Modbus endpoint. Each time a supporting endpoint handler is created
+ * an instance of this service will be created as well and attached to the
+ * thing handler.
+ *
+ * @author Nagy Attila Gabor - initial contribution
+ */
+@NonNullByDefault
+public interface ModbusThingHandlerDiscoveryService extends ThingHandlerService {
+
+    /**
+     * Implementation should start a discovery when this method gets called
+     *
+     * @param service the discovery service that should be called when the discovery is finished
+     * @return returns true if discovery is enabled, false otherwise
+     */
+    public boolean startScan(ModbusDiscoveryService service);
+
+    /**
+     * This method should return true, if an async scan is in progress
+     *
+     * @return true if a scan is in progress false otherwise
+     */
+    public boolean scanInProgress();
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/handler/EndpointNotInitializedException.java

@@ -0,0 +1,27 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.handler;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+
+/**
+ * Signals that {@link ModbusEndpointThingHandler} is not properly initialized yet, and the requested operation cannot
+ * be completed.
+ *
+ * @author Sami Salonen - Initial contribution
+ */
+@NonNullByDefault
+public class EndpointNotInitializedException extends Exception {
+
+    private static final long serialVersionUID = -6721646244844348903L;
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/handler/ModbusEndpointThingHandler.java

@@ -0,0 +1,53 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.handler;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+import org.openhab.core.common.registry.Identifiable;
+import org.openhab.core.thing.ThingUID;
+import org.openhab.io.transport.modbus.ModbusCommunicationInterface;
+
+/**
+ * Base interface for thing handlers of endpoint things
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ */
+@NonNullByDefault
+public interface ModbusEndpointThingHandler extends Identifiable<ThingUID> {
+
+    /**
+     * Gets the {@link ModbusCommunicationInterface} represented by the thing
+     *
+     * Note that this can be <code>null</code> in case of incomplete initialization
+     *
+     * @return communication interface represented by this thing handler
+     */
+    public @Nullable ModbusCommunicationInterface getCommunicationInterface();
+
+    /**
+     * Get Slave ID, also called as unit id, represented by the thing
+     *
+     * @return slave id represented by this thing handler
+     * @throws EndpointNotInitializedException in case the initialization is not complete
+     */
+    public int getSlaveId() throws EndpointNotInitializedException;
+
+    /**
+     * Return true if auto discovery is enabled for this endpoint
+     *
+     * @return boolean true if the discovery is enabled
+     */
+    public boolean isDiscoveryEnabled();
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/handler/ModbusPollerThingHandler.java

@@ -0,0 +1,442 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.handler;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.stream.Collectors;
+
+import org.apache.commons.lang.StringUtils;
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+import org.openhab.binding.modbus.internal.AtomicStampedValue;
+import org.openhab.binding.modbus.internal.ModbusBindingConstantsInternal;
+import org.openhab.binding.modbus.internal.config.ModbusPollerConfiguration;
+import org.openhab.binding.modbus.internal.handler.ModbusDataThingHandler;
+import org.openhab.core.thing.Bridge;
+import org.openhab.core.thing.ChannelUID;
+import org.openhab.core.thing.Thing;
+import org.openhab.core.thing.ThingStatus;
+import org.openhab.core.thing.ThingStatusDetail;
+import org.openhab.core.thing.ThingStatusInfo;
+import org.openhab.core.thing.binding.BaseBridgeHandler;
+import org.openhab.core.thing.binding.ThingHandler;
+import org.openhab.core.types.Command;
+import org.openhab.io.transport.modbus.AsyncModbusFailure;
+import org.openhab.io.transport.modbus.AsyncModbusReadResult;
+import org.openhab.io.transport.modbus.ModbusCommunicationInterface;
+import org.openhab.io.transport.modbus.ModbusConstants;
+import org.openhab.io.transport.modbus.ModbusFailureCallback;
+import org.openhab.io.transport.modbus.ModbusReadCallback;
+import org.openhab.io.transport.modbus.ModbusReadFunctionCode;
+import org.openhab.io.transport.modbus.ModbusReadRequestBlueprint;
+import org.openhab.io.transport.modbus.PollTask;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * The {@link ModbusPollerThingHandler} is responsible for polling Modbus slaves. Errors and data is delegated to
+ * child thing handlers inheriting from {@link ModbusReadCallback} -- in practice: {@link ModbusDataThingHandler}.
+ *
+ * @author Sami Salonen - Initial contribution
+ */
+@NonNullByDefault
+public class ModbusPollerThingHandler extends BaseBridgeHandler {
+
+    /**
+     * {@link ModbusReadCallback} that delegates all tasks forward.
+     *
+     * All instances of {@linkplain ReadCallbackDelegator} are considered equal, if they are connected to the same
+     * bridge. This makes sense, as the callback delegates
+     * to all child things of this bridge.
+     *
+     * @author Sami Salonen
+     *
+     */
+    private class ReadCallbackDelegator
+            implements ModbusReadCallback, ModbusFailureCallback<ModbusReadRequestBlueprint> {
+
+        private volatile @Nullable AtomicStampedValue<PollResult> lastResult;
+
+        public synchronized void handleResult(PollResult result) {
+            // Ignore all incoming data and errors if configuration is not correct
+            if (hasConfigurationError() || disposed) {
+                return;
+            }
+            if (config.getCacheMillis() >= 0) {
+                AtomicStampedValue<PollResult> localLastResult = this.lastResult;
+                if (localLastResult == null) {
+                    this.lastResult = new AtomicStampedValue<>(System.currentTimeMillis(), result);
+                } else {
+                    localLastResult.update(System.currentTimeMillis(), result);
+                    this.lastResult = localLastResult;
+                }
+            }
+            logger.debug("Thing {} received response {}", thing.getUID(), result);
+            notifyChildren(result);
+            if (result.failure != null) {
+                Exception error = result.failure.getCause();
+                assert error != null;
+                updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.COMMUNICATION_ERROR,
+                        String.format("Error with read: %s: %s", error.getClass().getName(), error.getMessage()));
+            } else {
+                resetCommunicationError();
+            }
+        }
+
+        @Override
+        public synchronized void handle(AsyncModbusReadResult result) {
+            handleResult(new PollResult(result));
+        }
+
+        @Override
+        public synchronized void handle(AsyncModbusFailure<ModbusReadRequestBlueprint> failure) {
+            handleResult(new PollResult(failure));
+        }
+
+        private void resetCommunicationError() {
+            ThingStatusInfo statusInfo = thing.getStatusInfo();
+            if (ThingStatus.OFFLINE.equals(statusInfo.getStatus())
+                    && ThingStatusDetail.COMMUNICATION_ERROR.equals(statusInfo.getStatusDetail())) {
+                updateStatus(ThingStatus.ONLINE);
+            }
+        }
+
+        /**
+         * Update children data if data is fresh enough
+         *
+         * @param oldestStamp oldest data that is still passed to children
+         * @return whether data was updated. Data is not updated when it's too old or there's no data at all.
+         */
+        @SuppressWarnings("null")
+        public boolean updateChildrenWithOldData(long oldestStamp) {
+            return Optional.ofNullable(this.lastResult).map(result -> result.copyIfStampAfter(oldestStamp))
+                    .map(result -> {
+                        logger.debug("Thing {} reusing cached data: {}", thing.getUID(), result.getValue());
+                        notifyChildren(result.getValue());
+                        return true;
+                    }).orElse(false);
+        }
+
+        private void notifyChildren(PollResult pollResult) {
+            @Nullable
+            AsyncModbusReadResult result = pollResult.result;
+            @Nullable
+            AsyncModbusFailure<ModbusReadRequestBlueprint> failure = pollResult.failure;
+            childCallbacks.forEach(handler -> {
+                if (result != null) {
+                    handler.onReadResult(result);
+                } else if (failure != null) {
+                    handler.handleReadError(failure);
+                }
+            });
+        }
+
+        /**
+         * Rest data caches
+         */
+        public void resetCache() {
+            lastResult = null;
+        }
+    }
+
+    /**
+     * Immutable data object to cache the results of a poll request
+     */
+    private class PollResult {
+
+        public final @Nullable AsyncModbusReadResult result;
+        public final @Nullable AsyncModbusFailure<ModbusReadRequestBlueprint> failure;
+
+        PollResult(AsyncModbusReadResult result) {
+            this.result = result;
+            this.failure = null;
+        }
+
+        PollResult(AsyncModbusFailure<ModbusReadRequestBlueprint> failure) {
+            this.result = null;
+            this.failure = failure;
+        }
+
+        @Override
+        public String toString() {
+            return failure == null ? String.format("PollResult(result=%s)", result)
+                    : String.format("PollResult(failure=%s)", failure);
+        }
+    }
+
+    private final Logger logger = LoggerFactory.getLogger(ModbusPollerThingHandler.class);
+
+    private final static List<String> SORTED_READ_FUNCTION_CODES = ModbusBindingConstantsInternal.READ_FUNCTION_CODES
+            .keySet().stream().sorted().collect(Collectors.toList());
+
+    private @NonNullByDefault({}) ModbusPollerConfiguration config;
+    private long cacheMillis;
+    private volatile @Nullable PollTask pollTask;
+    private volatile @Nullable ModbusReadRequestBlueprint request;
+    private volatile boolean disposed;
+    private volatile List<ModbusDataThingHandler> childCallbacks = new CopyOnWriteArrayList<>();
+    private @NonNullByDefault({}) ModbusCommunicationInterface comms;
+
+    private ReadCallbackDelegator callbackDelegator = new ReadCallbackDelegator();
+
+    private @Nullable ModbusReadFunctionCode functionCode;
+
+    public ModbusPollerThingHandler(Bridge bridge) {
+        super(bridge);
+    }
+
+    @Override
+    public void handleCommand(ChannelUID channelUID, Command command) {
+        // No channels, no commands
+    }
+
+    private @Nullable ModbusEndpointThingHandler getEndpointThingHandler() {
+        Bridge bridge = getBridge();
+        if (bridge == null) {
+            logger.debug("Bridge is null");
+            return null;
+        }
+        if (bridge.getStatus() != ThingStatus.ONLINE) {
+            logger.debug("Bridge is not online");
+            return null;
+        }
+
+        ThingHandler handler = bridge.getHandler();
+        if (handler == null) {
+            logger.debug("Bridge handler is null");
+            return null;
+        }
+
+        if (handler instanceof ModbusEndpointThingHandler) {
+            ModbusEndpointThingHandler slaveEndpoint = (ModbusEndpointThingHandler) handler;
+            return slaveEndpoint;
+        } else {
+            logger.debug("Unexpected bridge handler: {}", handler);
+            return null;
+        }
+    }
+
+    @Override
+    public synchronized void initialize() {
+        if (this.getThing().getStatus().equals(ThingStatus.ONLINE)) {
+            // If the bridge was online then first change it to offline.
+            // this ensures that children will be notified about the change
+            updateStatus(ThingStatus.OFFLINE);
+        }
+        this.callbackDelegator.resetCache();
+        comms = null;
+        request = null;
+        disposed = false;
+        logger.trace("Initializing {} from status {}", this.getThing().getUID(), this.getThing().getStatus());
+        try {
+            config = getConfigAs(ModbusPollerConfiguration.class);
+            String type = config.getType();
+            if (!ModbusBindingConstantsInternal.READ_FUNCTION_CODES.containsKey(type)) {
+                updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR,
+                        String.format("No function code found for type='%s'. Was expecting one of: %s", type,
+                                StringUtils.join(SORTED_READ_FUNCTION_CODES, ", ")));
+                return;
+            }
+            functionCode = ModbusBindingConstantsInternal.READ_FUNCTION_CODES.get(type);
+            switch (functionCode) {
+                case READ_INPUT_REGISTERS:
+                case READ_MULTIPLE_REGISTERS:
+                    if (config.getLength() > ModbusConstants.MAX_REGISTERS_READ_COUNT) {
+                        updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR, String.format(
+                                "Maximum of %d registers can be polled at once due to protocol limitations. Length %d is out of bounds.",
+                                ModbusConstants.MAX_REGISTERS_READ_COUNT, config.getLength()));
+                        return;
+                    }
+                    break;
+                case READ_COILS:
+                case READ_INPUT_DISCRETES:
+                    if (config.getLength() > ModbusConstants.MAX_BITS_READ_COUNT) {
+                        updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR, String.format(
+                                "Maximum of %d coils/discrete inputs can be polled at once due to protocol limitations. Length %d is out of bounds.",
+                                ModbusConstants.MAX_BITS_READ_COUNT, config.getLength()));
+                        return;
+                    }
+                    break;
+            }
+            cacheMillis = this.config.getCacheMillis();
+            registerPollTask();
+        } catch (EndpointNotInitializedException e) {
+            logger.debug("Exception during initialization", e);
+            updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR, String
+                    .format("Exception during initialization: %s (%s)", e.getMessage(), e.getClass().getSimpleName()));
+        } finally {
+            logger.trace("initialize() of thing {} '{}' finished", thing.getUID(), thing.getLabel());
+        }
+    }
+
+    @Override
+    public synchronized void dispose() {
+        logger.debug("dispose()");
+        // Mark handler as disposed as soon as possible to halt processing of callbacks
+        disposed = true;
+        unregisterPollTask();
+        this.callbackDelegator.resetCache();
+        comms = null;
+    }
+
+    /**
+     * Unregister poll task.
+     *
+     * No-op in case no poll task is registered, or if the initialization is incomplete.
+     */
+    public synchronized void unregisterPollTask() {
+        logger.trace("unregisterPollTask()");
+        if (config == null) {
+            return;
+        }
+        PollTask localPollTask = this.pollTask;
+        if (localPollTask != null) {
+            logger.debug("Unregistering polling from ModbusManager");
+            comms.unregisterRegularPoll(localPollTask);
+        }
+        this.pollTask = null;
+        request = null;
+        comms = null;
+        updateStatus(ThingStatus.OFFLINE);
+    }
+
+    /**
+     * Register poll task
+     *
+     * @throws EndpointNotInitializedException in case the bridge initialization is not complete. This should only
+     *             happen in transient conditions, for example, when bridge is initializing.
+     */
+    @SuppressWarnings("null")
+    private synchronized void registerPollTask() throws EndpointNotInitializedException {
+        logger.trace("registerPollTask()");
+        if (pollTask != null) {
+            updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR);
+            logger.debug("pollTask should be unregistered before registering a new one!");
+            return;
+        }
+
+        ModbusEndpointThingHandler slaveEndpointThingHandler = getEndpointThingHandler();
+        if (slaveEndpointThingHandler == null) {
+            updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.BRIDGE_OFFLINE, String.format("Bridge '%s' is offline",
+                    Optional.ofNullable(getBridge()).map(b -> b.getLabel()).orElse("<null>")));
+            logger.debug("No bridge handler available -- aborting init for {}", this);
+            return;
+        }
+        ModbusCommunicationInterface localComms = slaveEndpointThingHandler.getCommunicationInterface();
+        if (localComms == null) {
+            updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.BRIDGE_OFFLINE, String.format(
+                    "Bridge '%s' not completely initialized", Optional.ofNullable(getBridge()).map(b -> b.getLabel())));
+            logger.debug("Bridge not initialized fully (no communication interface) -- aborting init for {}", this);
+            return;
+        }
+        this.comms = localComms;
+        ModbusReadFunctionCode localFunctionCode = functionCode;
+        if (localFunctionCode == null) {
+            return;
+        }
+
+        ModbusReadRequestBlueprint localRequest = new ModbusReadRequestBlueprint(slaveEndpointThingHandler.getSlaveId(),
+                localFunctionCode, config.getStart(), config.getLength(), config.getMaxTries());
+        this.request = localRequest;
+
+        if (config.getRefresh() <= 0L) {
+            logger.debug("Not registering polling with ModbusManager since refresh disabled");
+            updateStatus(ThingStatus.ONLINE, ThingStatusDetail.NONE, "Not polling");
+        } else {
+            logger.debug("Registering polling with ModbusManager");
+            pollTask = localComms.registerRegularPoll(localRequest, config.getRefresh(), 0, callbackDelegator,
+                    callbackDelegator);
+            assert pollTask != null;
+            updateStatus(ThingStatus.ONLINE);
+        }
+    }
+
+    private boolean hasConfigurationError() {
+        ThingStatusInfo statusInfo = getThing().getStatusInfo();
+        return statusInfo.getStatus() == ThingStatus.OFFLINE
+                && statusInfo.getStatusDetail() == ThingStatusDetail.CONFIGURATION_ERROR;
+    }
+
+    @Override
+    public synchronized void bridgeStatusChanged(ThingStatusInfo bridgeStatusInfo) {
+        logger.debug("bridgeStatusChanged for {}. Reseting handler", this.getThing().getUID());
+        this.dispose();
+        this.initialize();
+    }
+
+    @Override
+    public void childHandlerInitialized(ThingHandler childHandler, Thing childThing) {
+        if (childHandler instanceof ModbusDataThingHandler) {
+            this.childCallbacks.add((ModbusDataThingHandler) childHandler);
+        }
+    }
+
+    @SuppressWarnings("unlikely-arg-type")
+    @Override
+    public void childHandlerDisposed(ThingHandler childHandler, Thing childThing) {
+        if (childHandler instanceof ModbusDataThingHandler) {
+            this.childCallbacks.remove(childHandler);
+        }
+    }
+
+    /**
+     * Return {@link ModbusReadRequestBlueprint} represented by this thing.
+     *
+     * Note that request might be <code>null</code> in case initialization is not complete.
+     *
+     * @return modbus request represented by this poller
+     */
+    public @Nullable ModbusReadRequestBlueprint getRequest() {
+        return request;
+    }
+
+    /**
+     * Get communication interface associated with this poller
+     *
+     * @return
+     */
+    public ModbusCommunicationInterface getCommunicationInterface() {
+        return comms;
+    }
+
+    /**
+     * Refresh the data
+     *
+     * If data or error was just recently received (i.e. cache is fresh), return the cached response.
+     */
+    public void refresh() {
+        ModbusReadRequestBlueprint localRequest = this.request;
+        if (localRequest == null) {
+            return;
+        }
+
+        long oldDataThreshold = System.currentTimeMillis() - cacheMillis;
+        boolean cacheWasRecentEnoughForUpdate = cacheMillis > 0
+                && this.callbackDelegator.updateChildrenWithOldData(oldDataThreshold);
+        if (cacheWasRecentEnoughForUpdate) {
+            logger.debug(
+                    "Poller {} received refresh() and cache was recent enough (age at most {} ms). Reusing old response",
+                    getThing().getUID(), cacheMillis);
+        } else {
+            // cache expired, poll new data
+            logger.debug("Poller {} received refresh() but the cache is not applicable. Polling new data",
+                    getThing().getUID());
+            ModbusCommunicationInterface localComms = comms;
+            if (localComms != null) {
+                localComms.submitOneTimePoll(localRequest, callbackDelegator, callbackDelegator);
+            }
+        }
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/AtomicStampedValue.java

@@ -0,0 +1,137 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal;
+
+import java.util.Objects;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+
+/**
+ * Timestamp-value pair that can be updated atomically
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ * @param <V> type of the value
+ */
+@NonNullByDefault
+public class AtomicStampedValue<V> implements Cloneable {
+
+    private long stamp;
+    private V value;
+
+    private AtomicStampedValue(AtomicStampedValue<V> copy) {
+        this(copy.stamp, copy.value);
+    }
+
+    /**
+     * Construct new stamped key-value pair
+     *
+     * @param stamp stamp for the data
+     * @param value value for the data
+     *
+     * @throws NullPointerException when key or value is null
+     */
+    public AtomicStampedValue(long stamp, V value) {
+        Objects.requireNonNull(value, "value should not be null!");
+        this.stamp = stamp;
+        this.value = value;
+    }
+
+    /**
+     * Update data in this instance atomically
+     *
+     * @param stamp stamp for the data
+     * @param value value for the data
+     *
+     * @throws NullPointerException when value is null
+     */
+    public synchronized void update(long stamp, V value) {
+        Objects.requireNonNull(value, "value should not be null!");
+        this.stamp = stamp;
+        this.value = value;
+    }
+
+    /**
+     * Copy data atomically and return the new (shallow) copy
+     *
+     * @return new copy of the data
+     * @throws CloneNotSupportedException
+     */
+    @SuppressWarnings("unchecked")
+    public synchronized AtomicStampedValue<V> copy() {
+        return (AtomicStampedValue<V>) this.clone();
+    }
+
+    /**
+     * Synchronized implementation of clone with exception swallowing
+     */
+    @Override
+    protected synchronized Object clone() {
+        try {
+            return super.clone();
+        } catch (CloneNotSupportedException e) {
+            // We should never end up here since this class implements Cloneable
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * Copy data atomically if data is after certain stamp ("fresh" enough)
+     *
+     * @param stampMin
+     * @return null, if the stamp of this instance is before stampMin. Otherwise return the data copied
+     */
+    public synchronized @Nullable AtomicStampedValue<V> copyIfStampAfter(long stampMin) {
+        if (stampMin <= this.stamp) {
+            return new AtomicStampedValue<>(this);
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Get stamp
+     */
+    public long getStamp() {
+        return stamp;
+    }
+
+    /**
+     * Get value
+     */
+    public V getValue() {
+        return value;
+    }
+
+    /**
+     * Compare two AtomicStampedKeyValue objects based on stamps
+     *
+     * Nulls are ordered first
+     *
+     * @param x first instance
+     * @param y second instance
+     * @return a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater
+     *         than the second.
+     */
+    public static int compare(@SuppressWarnings("rawtypes") @Nullable AtomicStampedValue x,
+            @SuppressWarnings("rawtypes") @Nullable AtomicStampedValue y) {
+        if (x == null) {
+            return -1;
+        } else if (y == null) {
+            return 1;
+        } else {
+            return Long.compare(x.stamp, y.stamp);
+        }
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/ModbusBindingConstantsInternal.java

@@ -0,0 +1,77 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal;
+
+import static org.openhab.binding.modbus.ModbusBindingConstants.BINDING_ID;
+
+import java.util.HashMap;
+import java.util.Map;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.core.thing.ThingTypeUID;
+import org.openhab.io.transport.modbus.ModbusReadFunctionCode;
+
+/**
+ * The {@link ModbusBinding} class defines common constants, which are
+ * used across the whole binding.
+ *
+ * @author Sami Salonen - Initial contribution
+ */
+@NonNullByDefault
+public class ModbusBindingConstantsInternal {
+
+    // List of all Thing Type UIDs
+    public static final ThingTypeUID THING_TYPE_MODBUS_TCP = new ThingTypeUID(BINDING_ID, "tcp");
+    public static final ThingTypeUID THING_TYPE_MODBUS_SERIAL = new ThingTypeUID(BINDING_ID, "serial");
+    public static final ThingTypeUID THING_TYPE_MODBUS_POLLER = new ThingTypeUID(BINDING_ID, "poller");
+    public static final ThingTypeUID THING_TYPE_MODBUS_DATA = new ThingTypeUID(BINDING_ID, "data");
+
+    // List of all Channel ids
+    public static final String CHANNEL_SWITCH = "switch";
+    public static final String CHANNEL_CONTACT = "contact";
+    public static final String CHANNEL_DATETIME = "datetime";
+    public static final String CHANNEL_DIMMER = "dimmer";
+    public static final String CHANNEL_NUMBER = "number";
+    public static final String CHANNEL_STRING = "string";
+    public static final String CHANNEL_ROLLERSHUTTER = "rollershutter";
+    public static final String CHANNEL_LAST_READ_SUCCESS = "lastReadSuccess";
+    public static final String CHANNEL_LAST_READ_ERROR = "lastReadError";
+    public static final String CHANNEL_LAST_WRITE_SUCCESS = "lastWriteSuccess";
+    public static final String CHANNEL_LAST_WRITE_ERROR = "lastWriteError";
+
+    public static final String[] DATA_CHANNELS = { CHANNEL_SWITCH, CHANNEL_CONTACT, CHANNEL_DATETIME, CHANNEL_DIMMER,
+            CHANNEL_NUMBER, CHANNEL_STRING, CHANNEL_ROLLERSHUTTER };
+
+    public static final String[] DATA_CHANNELS_TO_COPY_FROM_READ_TO_READWRITE = { CHANNEL_SWITCH, CHANNEL_CONTACT,
+            CHANNEL_DATETIME, CHANNEL_DIMMER, CHANNEL_NUMBER, CHANNEL_STRING, CHANNEL_ROLLERSHUTTER,
+            CHANNEL_LAST_READ_SUCCESS, CHANNEL_LAST_READ_ERROR };
+
+    public static final String[] DATA_CHANNELS_TO_DELEGATE_COMMAND_FROM_READWRITE_TO_WRITE = { CHANNEL_SWITCH,
+            CHANNEL_CONTACT, CHANNEL_DATETIME, CHANNEL_DIMMER, CHANNEL_NUMBER, CHANNEL_STRING, CHANNEL_ROLLERSHUTTER };
+
+    public static final String WRITE_TYPE_COIL = "coil";
+    public static final String WRITE_TYPE_HOLDING = "holding";
+
+    public static final String READ_TYPE_COIL = "coil";
+    public static final String READ_TYPE_HOLDING_REGISTER = "holding";
+    public static final String READ_TYPE_DISCRETE_INPUT = "discrete";
+    public static final String READ_TYPE_INPUT_REGISTER = "input";
+
+    public static final Map<String, ModbusReadFunctionCode> READ_FUNCTION_CODES = new HashMap<>();
+    static {
+        READ_FUNCTION_CODES.put(READ_TYPE_COIL, ModbusReadFunctionCode.READ_COILS);
+        READ_FUNCTION_CODES.put(READ_TYPE_DISCRETE_INPUT, ModbusReadFunctionCode.READ_INPUT_DISCRETES);
+        READ_FUNCTION_CODES.put(READ_TYPE_INPUT_REGISTER, ModbusReadFunctionCode.READ_INPUT_REGISTERS);
+        READ_FUNCTION_CODES.put(READ_TYPE_HOLDING_REGISTER, ModbusReadFunctionCode.READ_MULTIPLE_REGISTERS);
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/ModbusConfigurationException.java

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+
+/**
+ * Exception for binding configuration exceptions
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ */
+@NonNullByDefault
+public class ModbusConfigurationException extends Exception {
+
+    public ModbusConfigurationException(String errmsg) {
+        super(errmsg);
+    }
+
+    private static final long serialVersionUID = -466597103876477780L;
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/ModbusHandlerFactory.java

@@ -0,0 +1,96 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal;
+
+import static org.openhab.binding.modbus.internal.ModbusBindingConstantsInternal.*;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+import org.openhab.binding.modbus.handler.ModbusPollerThingHandler;
+import org.openhab.binding.modbus.internal.handler.ModbusDataThingHandler;
+import org.openhab.binding.modbus.internal.handler.ModbusSerialThingHandler;
+import org.openhab.binding.modbus.internal.handler.ModbusTcpThingHandler;
+import org.openhab.core.thing.Bridge;
+import org.openhab.core.thing.Thing;
+import org.openhab.core.thing.ThingTypeUID;
+import org.openhab.core.thing.binding.BaseThingHandlerFactory;
+import org.openhab.core.thing.binding.ThingHandler;
+import org.openhab.core.thing.binding.ThingHandlerFactory;
+import org.openhab.io.transport.modbus.ModbusManager;
+import org.osgi.service.component.annotations.Component;
+import org.osgi.service.component.annotations.Reference;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * The {@link ModbusHandlerFactory} is responsible for creating things and thing
+ * handlers.
+ *
+ * @author Sami Salonen - Initial contribution
+ */
+@Component(service = ThingHandlerFactory.class, configurationPid = "binding.modbus")
+@NonNullByDefault
+public class ModbusHandlerFactory extends BaseThingHandlerFactory {
+
+    private final Logger logger = LoggerFactory.getLogger(ModbusHandlerFactory.class);
+
+    private @NonNullByDefault({}) ModbusManager manager;
+
+    private static final Set<ThingTypeUID> SUPPORTED_THING_TYPES_UIDS = new HashSet<>();
+    static {
+        SUPPORTED_THING_TYPES_UIDS.add(THING_TYPE_MODBUS_TCP);
+        SUPPORTED_THING_TYPES_UIDS.add(THING_TYPE_MODBUS_SERIAL);
+        SUPPORTED_THING_TYPES_UIDS.add(THING_TYPE_MODBUS_POLLER);
+        SUPPORTED_THING_TYPES_UIDS.add(THING_TYPE_MODBUS_DATA);
+    }
+
+    @Override
+    public boolean supportsThingType(ThingTypeUID thingTypeUID) {
+        return SUPPORTED_THING_TYPES_UIDS.contains(thingTypeUID);
+    }
+
+    @Override
+    protected @Nullable ThingHandler createHandler(Thing thing) {
+        ThingTypeUID thingTypeUID = thing.getThingTypeUID();
+        if (thingTypeUID.equals(THING_TYPE_MODBUS_TCP)) {
+            logger.debug("createHandler Modbus tcp");
+            return new ModbusTcpThingHandler((Bridge) thing, manager);
+        } else if (thingTypeUID.equals(THING_TYPE_MODBUS_SERIAL)) {
+            logger.debug("createHandler Modbus serial");
+            return new ModbusSerialThingHandler((Bridge) thing, manager);
+        } else if (thingTypeUID.equals(THING_TYPE_MODBUS_POLLER)) {
+            logger.debug("createHandler Modbus poller");
+            return new ModbusPollerThingHandler((Bridge) thing);
+        } else if (thingTypeUID.equals(THING_TYPE_MODBUS_DATA)) {
+            logger.debug("createHandler data");
+            return new ModbusDataThingHandler(thing);
+        }
+        logger.error("createHandler for unknown thing type uid {}. Thing label was: {}", thing.getThingTypeUID(),
+                thing.getLabel());
+
+        return null;
+    }
+
+    @Reference
+    public void setModbusManager(ModbusManager manager) {
+        logger.debug("Setting manager: {}", manager);
+        this.manager = manager;
+    }
+
+    public void unsetModbusManager(ModbusManager manager) {
+        this.manager = null;
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/Transformation.java

@@ -0,0 +1,223 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal;
+
+import static org.apache.commons.lang.StringUtils.isEmpty;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.apache.commons.lang.builder.EqualsBuilder;
+import org.apache.commons.lang.builder.StandardToStringStyle;
+import org.apache.commons.lang.builder.ToStringBuilder;
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+import org.openhab.core.library.types.DecimalType;
+import org.openhab.core.library.types.OnOffType;
+import org.openhab.core.library.types.OpenClosedType;
+import org.openhab.core.transform.TransformationException;
+import org.openhab.core.transform.TransformationHelper;
+import org.openhab.core.transform.TransformationService;
+import org.openhab.core.types.Command;
+import org.openhab.core.types.State;
+import org.openhab.core.types.TypeParser;
+import org.osgi.framework.BundleContext;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Class describing transformation of a command or state.
+ *
+ * Inspired from other openHAB binding "Transformation" classes.
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ */
+@NonNullByDefault
+public class Transformation {
+
+    public static final String TRANSFORM_DEFAULT = "default";
+    public static final Transformation IDENTITY_TRANSFORMATION = new Transformation(TRANSFORM_DEFAULT, null, null);
+
+    /** RegEx to extract and parse a function String <code>'(.*?)\((.*)\)'</code> */
+    private static final Pattern EXTRACT_FUNCTION_PATTERN = Pattern.compile("(?<service>.*?)\\((?<arg>.*)\\)");
+
+    /**
+     * Ordered list of types that are tried out first when trying to parse transformed command
+     */
+    private static final List<Class<? extends Command>> DEFAULT_TYPES = new ArrayList<>();
+    static {
+        DEFAULT_TYPES.add(DecimalType.class);
+        DEFAULT_TYPES.add(OpenClosedType.class);
+        DEFAULT_TYPES.add(OnOffType.class);
+    }
+
+    private final Logger logger = LoggerFactory.getLogger(Transformation.class);
+
+    private static StandardToStringStyle toStringStyle = new StandardToStringStyle();
+
+    static {
+        toStringStyle.setUseShortClassName(true);
+    }
+
+    private final @Nullable String transformation;
+    private final @Nullable String transformationServiceName;
+    private final @Nullable String transformationServiceParam;
+
+    /**
+     *
+     * @param transformation either FUN(VAL) (standard transformation syntax), default (identity transformation
+     *            (output equals input)) or some other value (output is a constant). Futhermore, empty string is
+     *            considered the same way as "default".
+     */
+    public Transformation(@Nullable String transformation) {
+        this.transformation = transformation;
+        //
+        // Parse transformation configuration here on construction, but delay the
+        // construction of TransformationService to call-time
+        if (isEmpty(transformation) || transformation.equalsIgnoreCase(TRANSFORM_DEFAULT)) {
+            // no-op (identity) transformation
+            transformationServiceName = null;
+            transformationServiceParam = null;
+        } else {
+            Matcher matcher = EXTRACT_FUNCTION_PATTERN.matcher(transformation);
+            if (matcher.matches()) {
+                matcher.reset();
+                matcher.find();
+                transformationServiceName = matcher.group("service");
+                transformationServiceParam = matcher.group("arg");
+            } else {
+                logger.debug(
+                        "Given transformation configuration '{}' did not match the FUN(VAL) pattern. Transformation output will be constant '{}'",
+                        transformation, transformation);
+                transformationServiceName = null;
+                transformationServiceParam = null;
+            }
+        }
+    }
+
+    /**
+     * For testing, thus package visibility by design
+     *
+     * @param transformation
+     * @param transformationServiceName
+     * @param transformationServiceParam
+     */
+    Transformation(String transformation, @Nullable String transformationServiceName,
+            @Nullable String transformationServiceParam) {
+        this.transformation = transformation;
+        this.transformationServiceName = transformationServiceName;
+        this.transformationServiceParam = transformationServiceParam;
+    }
+
+    public String transform(BundleContext context, String value) {
+        String transformedResponse;
+        String transformationServiceName = this.transformationServiceName;
+        String transformationServiceParam = this.transformationServiceParam;
+
+        if (transformationServiceName != null) {
+            try {
+                if (transformationServiceParam == null) {
+                    throw new TransformationException(
+                            "transformation service parameter is missing! Invalid transform?");
+                }
+                @Nullable
+                TransformationService transformationService = TransformationHelper.getTransformationService(context,
+                        transformationServiceName);
+                if (transformationService != null) {
+                    transformedResponse = transformationService.transform(transformationServiceParam, value);
+                } else {
+                    transformedResponse = value;
+                    logger.warn("couldn't transform response because transformationService of type '{}' is unavailable",
+                            transformationServiceName);
+                }
+            } catch (TransformationException te) {
+                logger.error("transformation throws exception [transformation={}, response={}]", transformation, value,
+                        te);
+
+                // in case of an error we return the response without any
+                // transformation
+                transformedResponse = value;
+            }
+        } else if (isIdentityTransform()) {
+            // identity transformation
+            transformedResponse = value;
+        } else {
+            // pass value as is
+            transformedResponse = this.transformation;
+        }
+
+        return transformedResponse == null ? "" : transformedResponse;
+    }
+
+    public boolean isIdentityTransform() {
+        return TRANSFORM_DEFAULT.equalsIgnoreCase(this.transformation);
+    }
+
+    public static Optional<Command> tryConvertToCommand(String transformed) {
+        Optional<Command> transformedCommand = Optional.ofNullable(TypeParser.parseCommand(DEFAULT_TYPES, transformed));
+        return transformedCommand;
+    }
+
+    /**
+     * Transform state to another state using this transformation
+     *
+     * @param context
+     * @param types types to used to parse the transformation result
+     * @param command
+     * @return Transformed command, or null if no transformation was possible
+     */
+    public @Nullable State transformState(BundleContext context, List<Class<? extends State>> types, State state) {
+        // Note that even identity transformations go through the State -> String -> State steps. This does add some
+        // overhead but takes care of DecimalType -> PercentType conversions, for example.
+        final String stateAsString = state.toString();
+        final String transformed = transform(context, stateAsString);
+        return TypeParser.parseState(types, transformed);
+    }
+
+    public boolean hasTransformationService() {
+        return transformationServiceName != null;
+    }
+
+    @Override
+    public boolean equals(@Nullable Object obj) {
+        if (null == obj) {
+            return false;
+        }
+        if (this == obj) {
+            return true;
+        }
+        if (!(obj instanceof Transformation)) {
+            return false;
+        }
+        Transformation that = (Transformation) obj;
+        EqualsBuilder eb = new EqualsBuilder();
+        if (hasTransformationService()) {
+            eb.append(this.transformationServiceName, that.transformationServiceName);
+            eb.append(this.transformationServiceParam, that.transformationServiceParam);
+        } else {
+            eb.append(this.transformation, that.transformation);
+        }
+        return eb.isEquals();
+    }
+
+    @Override
+    public String toString() {
+        return new ToStringBuilder(this, toStringStyle).append("tranformation", transformation)
+                .append("transformationServiceName", transformationServiceName)
+                .append("transformationServiceParam", transformationServiceParam).toString();
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/config/ModbusDataConfiguration.java

@@ -0,0 +1,117 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal.config;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+
+/**
+ * Configuration for data thing
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ */
+@NonNullByDefault
+public class ModbusDataConfiguration {
+
+    private @Nullable String readStart;
+    private @Nullable String readTransform;
+    private @Nullable String readValueType;
+    private @Nullable String writeStart;
+    private @Nullable String writeType;
+    private @Nullable String writeTransform;
+    private @Nullable String writeValueType;
+    private boolean writeMultipleEvenWithSingleRegisterOrCoil;
+    private int writeMaxTries = 3; // backwards compatibility and tests
+    private long updateUnchangedValuesEveryMillis = 1000L;
+
+    public @Nullable String getReadStart() {
+        return readStart;
+    }
+
+    public void setReadStart(String readStart) {
+        this.readStart = readStart;
+    }
+
+    public @Nullable String getReadTransform() {
+        return readTransform;
+    }
+
+    public void setReadTransform(String readTransform) {
+        this.readTransform = readTransform;
+    }
+
+    public @Nullable String getReadValueType() {
+        return readValueType;
+    }
+
+    public void setReadValueType(String readValueType) {
+        this.readValueType = readValueType;
+    }
+
+    public @Nullable String getWriteStart() {
+        return writeStart;
+    }
+
+    public void setWriteStart(String writeStart) {
+        this.writeStart = writeStart;
+    }
+
+    public @Nullable String getWriteType() {
+        return writeType;
+    }
+
+    public void setWriteType(String writeType) {
+        this.writeType = writeType;
+    }
+
+    public @Nullable String getWriteTransform() {
+        return writeTransform;
+    }
+
+    public void setWriteTransform(String writeTransform) {
+        this.writeTransform = writeTransform;
+    }
+
+    public @Nullable String getWriteValueType() {
+        return writeValueType;
+    }
+
+    public void setWriteValueType(String writeValueType) {
+        this.writeValueType = writeValueType;
+    }
+
+    public boolean isWriteMultipleEvenWithSingleRegisterOrCoil() {
+        return writeMultipleEvenWithSingleRegisterOrCoil;
+    }
+
+    public void setWriteMultipleEvenWithSingleRegisterOrCoil(boolean writeMultipleEvenWithSingleRegisterOrCoil) {
+        this.writeMultipleEvenWithSingleRegisterOrCoil = writeMultipleEvenWithSingleRegisterOrCoil;
+    }
+
+    public int getWriteMaxTries() {
+        return writeMaxTries;
+    }
+
+    public void setWriteMaxTries(int writeMaxTries) {
+        this.writeMaxTries = writeMaxTries;
+    }
+
+    public long getUpdateUnchangedValuesEveryMillis() {
+        return updateUnchangedValuesEveryMillis;
+    }
+
+    public void setUpdateUnchangedValuesEveryMillis(long updateUnchangedValuesEveryMillis) {
+        this.updateUnchangedValuesEveryMillis = updateUnchangedValuesEveryMillis;
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/config/ModbusPollerConfiguration.java

@@ -0,0 +1,118 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal.config;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+
+/**
+ * Configuration for poller thing
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ */
+@NonNullByDefault
+public class ModbusPollerConfiguration {
+    private long refresh;
+    private int start;
+    private int length;
+    private @Nullable String type;
+    private int maxTries = 3;// backwards compatibility and tests
+    private long cacheMillis = 50L;
+
+    /**
+     * Gets refresh period in milliseconds
+     */
+    public long getRefresh() {
+        return refresh;
+    }
+
+    /**
+     * Sets refresh period in milliseconds
+     */
+
+    public void setRefresh(long refresh) {
+        this.refresh = refresh;
+    }
+
+    /**
+     * Get address of the first register, coil, or discrete input to poll. Input as zero-based index number.
+     *
+     */
+    public int getStart() {
+        return start;
+    }
+
+    /**
+     * Sets address of the first register, coil, or discrete input to poll. Input as zero-based index number.
+     *
+     */
+    public void setStart(int start) {
+        this.start = start;
+    }
+
+    /**
+     * Gets number of registers, coils or discrete inputs to read.
+     */
+    public int getLength() {
+        return length;
+    }
+
+    /**
+     * Sets number of registers, coils or discrete inputs to read.
+     */
+    public void setLength(int length) {
+        this.length = length;
+    }
+
+    /**
+     * Gets type of modbus items to poll
+     *
+     */
+    public @Nullable String getType() {
+        return type;
+    }
+
+    /**
+     * Sets type of modbus items to poll
+     *
+     */
+    public void setType(String type) {
+        this.type = type;
+    }
+
+    public int getMaxTries() {
+        return maxTries;
+    }
+
+    public void setMaxTries(int maxTries) {
+        this.maxTries = maxTries;
+    }
+
+    /**
+     * Gets time to cache data.
+     *
+     * This is used for reusing cached data with explicit refresh calls.
+     */
+    public long getCacheMillis() {
+        return cacheMillis;
+    }
+
+    /**
+     * Sets time to cache data, in milliseconds
+     *
+     */
+    public void setCacheMillis(long cacheMillis) {
+        this.cacheMillis = cacheMillis;
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/config/ModbusSerialConfiguration.java

@@ -0,0 +1,161 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal.config;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+
+/**
+ * Configuration for serial thing
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ */
+@NonNullByDefault
+public class ModbusSerialConfiguration {
+    private @Nullable String port;
+    private int id;
+    private int baud;
+    private @Nullable String stopBits;
+    private @Nullable String parity;
+    private int dataBits;
+    private @Nullable String encoding;
+    private boolean echo;
+    private int receiveTimeoutMillis;
+    private @Nullable String flowControlIn;
+    private @Nullable String flowControlOut;
+    private int timeBetweenTransactionsMillis;
+    private int connectMaxTries;
+    private int connectTimeoutMillis;
+    private boolean enableDiscovery;
+
+    public @Nullable String getPort() {
+        return port;
+    }
+
+    public void setPort(String port) {
+        this.port = port;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public int getBaud() {
+        return baud;
+    }
+
+    public void setBaud(int baud) {
+        this.baud = baud;
+    }
+
+    public @Nullable String getStopBits() {
+        return stopBits;
+    }
+
+    public void setStopBits(String stopBits) {
+        this.stopBits = stopBits;
+    }
+
+    public @Nullable String getParity() {
+        return parity;
+    }
+
+    public void setParity(String parity) {
+        this.parity = parity;
+    }
+
+    public int getDataBits() {
+        return dataBits;
+    }
+
+    public void setDataBits(int dataBits) {
+        this.dataBits = dataBits;
+    }
+
+    public @Nullable String getEncoding() {
+        return encoding;
+    }
+
+    public void setEncoding(String encoding) {
+        this.encoding = encoding;
+    }
+
+    public boolean isEcho() {
+        return echo;
+    }
+
+    public void setEcho(boolean echo) {
+        this.echo = echo;
+    }
+
+    public int getReceiveTimeoutMillis() {
+        return receiveTimeoutMillis;
+    }
+
+    public void setReceiveTimeoutMillis(int receiveTimeoutMillis) {
+        this.receiveTimeoutMillis = receiveTimeoutMillis;
+    }
+
+    public @Nullable String getFlowControlIn() {
+        return flowControlIn;
+    }
+
+    public void setFlowControlIn(String flowControlIn) {
+        this.flowControlIn = flowControlIn;
+    }
+
+    public @Nullable String getFlowControlOut() {
+        return flowControlOut;
+    }
+
+    public void setFlowControlOut(String flowControlOut) {
+        this.flowControlOut = flowControlOut;
+    }
+
+    public int getTimeBetweenTransactionsMillis() {
+        return timeBetweenTransactionsMillis;
+    }
+
+    public void setTimeBetweenTransactionsMillis(int timeBetweenTransactionsMillis) {
+        this.timeBetweenTransactionsMillis = timeBetweenTransactionsMillis;
+    }
+
+    public int getConnectMaxTries() {
+        return connectMaxTries;
+    }
+
+    public void setConnectMaxTries(int connectMaxTries) {
+        this.connectMaxTries = connectMaxTries;
+    }
+
+    public int getConnectTimeoutMillis() {
+        return connectTimeoutMillis;
+    }
+
+    public void setConnectTimeoutMillis(int connectTimeoutMillis) {
+        this.connectTimeoutMillis = connectTimeoutMillis;
+    }
+
+    public boolean isDiscoveryEnabled() {
+        return enableDiscovery;
+    }
+
+    public void setDiscoveryEnabled(boolean enableDiscovery) {
+        this.enableDiscovery = enableDiscovery;
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/config/ModbusTcpConfiguration.java

@@ -0,0 +1,107 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal.config;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+
+/**
+ * Configuration for tcp thing
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ */
+@NonNullByDefault
+public class ModbusTcpConfiguration {
+    private @Nullable String host;
+    private int port;
+    private int id;
+    private int timeBetweenTransactionsMillis;
+    private int timeBetweenReconnectMillis;
+    private int connectMaxTries;
+    private int reconnectAfterMillis;
+    private int connectTimeoutMillis;
+    private boolean enableDiscovery;
+
+    public @Nullable String getHost() {
+        return host;
+    }
+
+    public void setHost(String host) {
+        this.host = host;
+    }
+
+    public int getPort() {
+        return port;
+    }
+
+    public void setPort(int port) {
+        this.port = port;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public int getTimeBetweenTransactionsMillis() {
+        return timeBetweenTransactionsMillis;
+    }
+
+    public void setTimeBetweenTransactionsMillis(int timeBetweenTransactionsMillis) {
+        this.timeBetweenTransactionsMillis = timeBetweenTransactionsMillis;
+    }
+
+    public int getTimeBetweenReconnectMillis() {
+        return timeBetweenReconnectMillis;
+    }
+
+    public void setTimeBetweenReconnectMillis(int timeBetweenReconnectMillis) {
+        this.timeBetweenReconnectMillis = timeBetweenReconnectMillis;
+    }
+
+    public int getConnectMaxTries() {
+        return connectMaxTries;
+    }
+
+    public void setConnectMaxTries(int connectMaxTries) {
+        this.connectMaxTries = connectMaxTries;
+    }
+
+    public int getReconnectAfterMillis() {
+        return reconnectAfterMillis;
+    }
+
+    public void setReconnectAfterMillis(int reconnectAfterMillis) {
+        this.reconnectAfterMillis = reconnectAfterMillis;
+    }
+
+    public int getConnectTimeoutMillis() {
+        return connectTimeoutMillis;
+    }
+
+    public void setConnectTimeoutMillis(int connectTimeoutMillis) {
+        this.connectTimeoutMillis = connectTimeoutMillis;
+    }
+
+    public boolean isDiscoveryEnabled() {
+        return enableDiscovery;
+    }
+
+    public void setDiscoveryEnabled(boolean enableDiscovery) {
+        this.enableDiscovery = enableDiscovery;
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/handler/AbstractModbusEndpointThingHandler.java

@@ -0,0 +1,131 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal.handler;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+import org.openhab.binding.modbus.handler.EndpointNotInitializedException;
+import org.openhab.binding.modbus.handler.ModbusEndpointThingHandler;
+import org.openhab.binding.modbus.internal.ModbusConfigurationException;
+import org.openhab.core.thing.Bridge;
+import org.openhab.core.thing.ChannelUID;
+import org.openhab.core.thing.ThingStatus;
+import org.openhab.core.thing.ThingStatusDetail;
+import org.openhab.core.thing.binding.BaseBridgeHandler;
+import org.openhab.core.types.Command;
+import org.openhab.io.transport.modbus.ModbusCommunicationInterface;
+import org.openhab.io.transport.modbus.ModbusManager;
+import org.openhab.io.transport.modbus.endpoint.EndpointPoolConfiguration;
+import org.openhab.io.transport.modbus.endpoint.ModbusSlaveEndpoint;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Base class for Modbus Slave endpoint thing handlers
+ *
+ * @author Sami Salonen - Initial contribution
+ *
+ * @param <E> endpoint class
+ * @param <C> config class
+ */
+@NonNullByDefault
+public abstract class AbstractModbusEndpointThingHandler<E extends ModbusSlaveEndpoint, C> extends BaseBridgeHandler
+        implements ModbusEndpointThingHandler {
+
+    protected volatile @Nullable C config;
+    protected volatile @Nullable E endpoint;
+    protected ModbusManager modbusManager;
+    protected volatile @Nullable EndpointPoolConfiguration poolConfiguration;
+    private final Logger logger = LoggerFactory.getLogger(AbstractModbusEndpointThingHandler.class);
+    private @NonNullByDefault({}) ModbusCommunicationInterface comms;
+
+    public AbstractModbusEndpointThingHandler(Bridge bridge, ModbusManager modbusManager) {
+        super(bridge);
+        this.modbusManager = modbusManager;
+    }
+
+    @Override
+    public void handleCommand(ChannelUID channelUID, Command command) {
+    }
+
+    @Override
+    public void initialize() {
+        synchronized (this) {
+            logger.trace("Initializing {} from status {}", this.getThing().getUID(), this.getThing().getStatus());
+            if (this.getThing().getStatus().equals(ThingStatus.ONLINE)) {
+                // If the bridge was online then first change it to offline.
+                // this ensures that children will be notified about the change
+                updateStatus(ThingStatus.OFFLINE);
+            }
+            try {
+                configure();
+                @Nullable
+                E endpoint = this.endpoint;
+                if (endpoint == null) {
+                    throw new IllegalStateException("endpoint null after configuration!");
+                }
+                try {
+                    comms = modbusManager.newModbusCommunicationInterface(endpoint, poolConfiguration);
+                    updateStatus(ThingStatus.ONLINE);
+                } catch (IllegalArgumentException e) {
+                    updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR,
+                            formatConflictingParameterError());
+                }
+            } catch (ModbusConfigurationException e) {
+                logger.debug("Exception during initialization", e);
+                updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR, String.format(
+                        "Exception during initialization: %s (%s)", e.getMessage(), e.getClass().getSimpleName()));
+            } finally {
+                logger.trace("initialize() of thing {} '{}' finished", thing.getUID(), thing.getLabel());
+            }
+        }
+    }
+
+    @Override
+    public void dispose() {
+        try {
+            ModbusCommunicationInterface localComms = comms;
+            if (localComms != null) {
+                localComms.close();
+            }
+        } catch (Exception e) {
+            logger.warn("Error closing modbus communication interface", e);
+        } finally {
+            comms = null;
+        }
+    }
+
+    @Override
+    public @Nullable ModbusCommunicationInterface getCommunicationInterface() {
+        return comms;
+    }
+
+    @Nullable
+    public E getEndpoint() {
+        return endpoint;
+    }
+
+    @Override
+    public abstract int getSlaveId() throws EndpointNotInitializedException;
+
+    /**
+     * Must be overriden by subclasses to initialize config, endpoint, and poolConfiguration
+     */
+    protected abstract void configure() throws ModbusConfigurationException;
+
+    /**
+     * Format error message in case some other endpoint has been configured with different
+     * {@link EndpointPoolConfiguration}
+     */
+    protected abstract String formatConflictingParameterError();
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/handler/ModbusDataThingHandler.java

@@ -0,0 +1,962 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal.handler;
+
+import static org.openhab.binding.modbus.internal.ModbusBindingConstantsInternal.*;
+
+import java.math.BigDecimal;
+import java.time.Duration;
+import java.time.LocalDateTime;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.concurrent.TimeUnit;
+
+import org.apache.commons.lang.NotImplementedException;
+import org.apache.commons.lang.StringUtils;
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+import org.openhab.binding.modbus.handler.EndpointNotInitializedException;
+import org.openhab.binding.modbus.handler.ModbusEndpointThingHandler;
+import org.openhab.binding.modbus.handler.ModbusPollerThingHandler;
+import org.openhab.binding.modbus.internal.ModbusBindingConstantsInternal;
+import org.openhab.binding.modbus.internal.ModbusConfigurationException;
+import org.openhab.binding.modbus.internal.Transformation;
+import org.openhab.binding.modbus.internal.config.ModbusDataConfiguration;
+import org.openhab.core.library.items.ContactItem;
+import org.openhab.core.library.items.DateTimeItem;
+import org.openhab.core.library.items.DimmerItem;
+import org.openhab.core.library.items.NumberItem;
+import org.openhab.core.library.items.RollershutterItem;
+import org.openhab.core.library.items.StringItem;
+import org.openhab.core.library.items.SwitchItem;
+import org.openhab.core.library.types.DateTimeType;
+import org.openhab.core.library.types.DecimalType;
+import org.openhab.core.library.types.OnOffType;
+import org.openhab.core.library.types.OpenClosedType;
+import org.openhab.core.thing.Bridge;
+import org.openhab.core.thing.ChannelUID;
+import org.openhab.core.thing.Thing;
+import org.openhab.core.thing.ThingStatus;
+import org.openhab.core.thing.ThingStatusDetail;
+import org.openhab.core.thing.ThingStatusInfo;
+import org.openhab.core.thing.binding.BaseThingHandler;
+import org.openhab.core.thing.binding.BridgeHandler;
+import org.openhab.core.thing.binding.ThingHandlerCallback;
+import org.openhab.core.types.Command;
+import org.openhab.core.types.RefreshType;
+import org.openhab.core.types.State;
+import org.openhab.core.types.UnDefType;
+import org.openhab.io.transport.modbus.AsyncModbusFailure;
+import org.openhab.io.transport.modbus.AsyncModbusReadResult;
+import org.openhab.io.transport.modbus.AsyncModbusWriteResult;
+import org.openhab.io.transport.modbus.BitArray;
+import org.openhab.io.transport.modbus.ModbusBitUtilities;
+import org.openhab.io.transport.modbus.ModbusCommunicationInterface;
+import org.openhab.io.transport.modbus.ModbusConstants;
+import org.openhab.io.transport.modbus.ModbusConstants.ValueType;
+import org.openhab.io.transport.modbus.ModbusReadFunctionCode;
+import org.openhab.io.transport.modbus.ModbusReadRequestBlueprint;
+import org.openhab.io.transport.modbus.ModbusRegisterArray;
+import org.openhab.io.transport.modbus.ModbusWriteCoilRequestBlueprint;
+import org.openhab.io.transport.modbus.ModbusWriteRegisterRequestBlueprint;
+import org.openhab.io.transport.modbus.ModbusWriteRequestBlueprint;
+import org.openhab.io.transport.modbus.exception.ModbusConnectionException;
+import org.openhab.io.transport.modbus.exception.ModbusTransportException;
+import org.openhab.io.transport.modbus.json.WriteRequestJsonUtilities;
+import org.osgi.framework.BundleContext;
+import org.osgi.framework.FrameworkUtil;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * The {@link ModbusDataThingHandler} is responsible for interpreting polled modbus data, as well as handling openHAB
+ * commands
+ *
+ * Thing can be re-initialized by the bridge in case of configuration changes (bridgeStatusChanged).
+ * Because of this, initialize, dispose and all callback methods (onRegisters, onBits, onError, onWriteResponse) are
+ * synchronized
+ * to avoid data race conditions.
+ *
+ * @author Sami Salonen - Initial contribution
+ */
+@NonNullByDefault
+public class ModbusDataThingHandler extends BaseThingHandler {
+
+    private final Logger logger = LoggerFactory.getLogger(ModbusDataThingHandler.class);
+
+    private final BundleContext bundleContext;
+
+    private static final Duration MIN_STATUS_INFO_UPDATE_INTERVAL = Duration.ofSeconds(1);
+    private static final Map<String, List<Class<? extends State>>> CHANNEL_ID_TO_ACCEPTED_TYPES = new HashMap<>();
+
+    static {
+        CHANNEL_ID_TO_ACCEPTED_TYPES.put(ModbusBindingConstantsInternal.CHANNEL_SWITCH,
+                new SwitchItem("").getAcceptedDataTypes());
+        CHANNEL_ID_TO_ACCEPTED_TYPES.put(ModbusBindingConstantsInternal.CHANNEL_CONTACT,
+                new ContactItem("").getAcceptedDataTypes());
+        CHANNEL_ID_TO_ACCEPTED_TYPES.put(ModbusBindingConstantsInternal.CHANNEL_DATETIME,
+                new DateTimeItem("").getAcceptedDataTypes());
+        CHANNEL_ID_TO_ACCEPTED_TYPES.put(ModbusBindingConstantsInternal.CHANNEL_DIMMER,
+                new DimmerItem("").getAcceptedDataTypes());
+        CHANNEL_ID_TO_ACCEPTED_TYPES.put(ModbusBindingConstantsInternal.CHANNEL_NUMBER,
+                new NumberItem("").getAcceptedDataTypes());
+        CHANNEL_ID_TO_ACCEPTED_TYPES.put(ModbusBindingConstantsInternal.CHANNEL_STRING,
+                new StringItem("").getAcceptedDataTypes());
+        CHANNEL_ID_TO_ACCEPTED_TYPES.put(ModbusBindingConstantsInternal.CHANNEL_ROLLERSHUTTER,
+                new RollershutterItem("").getAcceptedDataTypes());
+    }
+    // data channels + 4 for read/write last error/success
+    private static final int NUMER_OF_CHANNELS_HINT = CHANNEL_ID_TO_ACCEPTED_TYPES.size() + 4;
+
+    //
+    // If you change the below default/initial values, please update the corresponding values in dispose()
+    //
+    private volatile @Nullable ModbusDataConfiguration config;
+    private volatile @Nullable ValueType readValueType;
+    private volatile @Nullable ValueType writeValueType;
+    private volatile @Nullable Transformation readTransformation;
+    private volatile @Nullable Transformation writeTransformation;
+    private volatile Optional<Integer> readIndex = Optional.empty();
+    private volatile Optional<Integer> readSubIndex = Optional.empty();
+    private volatile @Nullable Integer writeStart;
+    private volatile int pollStart;
+    private volatile int slaveId;
+    private volatile @Nullable ModbusReadFunctionCode functionCode;
+    private volatile @Nullable ModbusReadRequestBlueprint readRequest;
+    private volatile long updateUnchangedValuesEveryMillis;
+    private volatile @NonNullByDefault({}) ModbusCommunicationInterface comms;
+    private volatile boolean isWriteEnabled;
+    private volatile boolean isReadEnabled;
+    private volatile boolean writeParametersHavingTransformationOnly;
+    private volatile boolean childOfEndpoint;
+    private volatile @Nullable ModbusPollerThingHandler pollerHandler;
+    private volatile Map<String, ChannelUID> channelCache = new HashMap<>();
+    private volatile Map<ChannelUID, Long> channelLastUpdated = new HashMap<>(NUMER_OF_CHANNELS_HINT);
+    private volatile Map<ChannelUID, State> channelLastState = new HashMap<>(NUMER_OF_CHANNELS_HINT);
+
+    private volatile LocalDateTime lastStatusInfoUpdate = LocalDateTime.MIN;
+    private volatile ThingStatusInfo statusInfo = new ThingStatusInfo(ThingStatus.UNKNOWN, ThingStatusDetail.NONE,
+            null);
+
+    public ModbusDataThingHandler(Thing thing) {
+        super(thing);
+        this.bundleContext = FrameworkUtil.getBundle(ModbusDataThingHandler.class).getBundleContext();
+    }
+
+    @Override
+    public synchronized void handleCommand(ChannelUID channelUID, Command command) {
+        logger.trace("Thing {} '{}' received command '{}' to channel '{}'", getThing().getUID(), getThing().getLabel(),
+                command, channelUID);
+        ModbusDataConfiguration config = this.config;
+        if (config == null) {
+            return;
+        }
+
+        if (RefreshType.REFRESH == command) {
+            ModbusPollerThingHandler poller = pollerHandler;
+            if (poller == null) {
+                // Data thing must be child of endpoint, and thus write-only.
+                // There is no data to update
+                return;
+            }
+            // We *schedule* the REFRESH to avoid dead-lock situation where poller is trying update this
+            // data thing with cached data (resulting in deadlock in two synchronized methods: this (handleCommand) and
+            // onRegisters.
+            scheduler.schedule(() -> poller.refresh(), 0, TimeUnit.SECONDS);
+            return;
+        } else if (hasConfigurationError()) {
+            logger.debug(
+                    "Thing {} '{}' command '{}' to channel '{}': Thing has configuration error so ignoring the command",
+                    getThing().getUID(), getThing().getLabel(), command, channelUID);
+            return;
+        } else if (!isWriteEnabled) {
+            logger.debug(
+                    "Thing {} '{}' command '{}' to channel '{}': no writing configured -> aborting processing command",
+                    getThing().getUID(), getThing().getLabel(), command, channelUID);
+            return;
+        }
+
+        Optional<Command> transformedCommand = transformCommandAndProcessJSON(channelUID, command);
+        if (transformedCommand == null) {
+            // We have, JSON as transform output (which has been processed) or some error. See
+            // transformCommandAndProcessJSON javadoc
+            return;
+        }
+
+        // We did not have JSON output from the transformation, so writeStart is absolute required. Abort if it is
+        // missing
+        Integer writeStart = this.writeStart;
+        if (writeStart == null) {
+            logger.debug(
+                    "Thing {} '{}': not processing command {} since writeStart is missing and transformation output is not a JSON",
+                    getThing().getUID(), getThing().getLabel(), command);
+            return;
+        }
+
+        if (!transformedCommand.isPresent()) {
+            // transformation failed, return
+            logger.warn("Cannot process command {} (of type {}) with channel {} since transformation was unsuccessful",
+                    command, command.getClass().getSimpleName(), channelUID);
+            return;
+        }
+
+        ModbusWriteRequestBlueprint request = requestFromCommand(channelUID, command, config, transformedCommand.get(),
+                writeStart);
+        if (request == null) {
+            return;
+        }
+
+        logger.trace("Submitting write task {} to endpoint {}", request, comms.getEndpoint());
+        comms.submitOneTimeWrite(request, this::onWriteResponse, this::handleWriteError);
+    }
+
+    /**
+     * Transform received command using the transformation.
+     *
+     * In case of JSON as transformation output, the output processed using {@link processJsonTransform}.
+     *
+     * @param channelUID channel UID corresponding to received command
+     * @param command command to be transformed
+     * @return transformed command. Null is returned with JSON transformation outputs and configuration errors
+     *
+     * @see processJsonTransform
+     */
+    private @Nullable Optional<Command> transformCommandAndProcessJSON(ChannelUID channelUID, Command command) {
+        String transformOutput;
+        Optional<Command> transformedCommand;
+        Transformation writeTransformation = this.writeTransformation;
+        if (writeTransformation == null || writeTransformation.isIdentityTransform()) {
+            transformedCommand = Optional.of(command);
+        } else {
+            transformOutput = writeTransformation.transform(bundleContext, command.toString());
+            if (transformOutput.contains("[")) {
+                processJsonTransform(command, transformOutput);
+                return null;
+            } else if (writeParametersHavingTransformationOnly) {
+                updateStatusIfChanged(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR, String.format(
+                        "Seems to have writeTransformation but no other write parameters. Since the transformation did not return a JSON for command '%s' (channel %s), this is a configuration error",
+                        command, channelUID));
+                return null;
+            } else {
+                transformedCommand = Transformation.tryConvertToCommand(transformOutput);
+                logger.trace("Converted transform output '{}' to command '{}' (type {})", transformOutput,
+                        transformedCommand.map(c -> c.toString()).orElse("<conversion failed>"),
+                        transformedCommand.map(c -> c.getClass().getName()).orElse("<conversion failed>"));
+            }
+        }
+        return transformedCommand;
+    }
+
+    private @Nullable ModbusWriteRequestBlueprint requestFromCommand(ChannelUID channelUID, Command origCommand,
+            ModbusDataConfiguration config, Command transformedCommand, Integer writeStart) {
+        ModbusWriteRequestBlueprint request;
+        boolean writeMultiple = config.isWriteMultipleEvenWithSingleRegisterOrCoil();
+        String writeType = config.getWriteType();
+        if (writeType == null) {
+            return null;
+        }
+        if (writeType.equals(WRITE_TYPE_COIL)) {
+            Optional<Boolean> commandAsBoolean = ModbusBitUtilities.translateCommand2Boolean(transformedCommand);
+            if (!commandAsBoolean.isPresent()) {
+                logger.warn(
+                        "Cannot process command {} with channel {} since command is not OnOffType, OpenClosedType or Decimal trying to write to coil. Do not know how to convert to 0/1. Transformed command was '{}'",
+                        origCommand, channelUID, transformedCommand);
+                return null;
+            }
+            boolean data = commandAsBoolean.get();
+            request = new ModbusWriteCoilRequestBlueprint(slaveId, writeStart, data, writeMultiple,
+                    config.getWriteMaxTries());
+        } else if (writeType.equals(WRITE_TYPE_HOLDING)) {
+            ValueType writeValueType = this.writeValueType;
+            if (writeValueType == null) {
+                // Should not happen in practice, since we are not in configuration error (checked above)
+                // This will make compiler happy anyways with the null checks
+                logger.warn("Received command but write value type not set! Ignoring command");
+                return null;
+            }
+            ModbusRegisterArray data = ModbusBitUtilities.commandToRegisters(transformedCommand, writeValueType);
+            writeMultiple = writeMultiple || data.size() > 1;
+            request = new ModbusWriteRegisterRequestBlueprint(slaveId, writeStart, data, writeMultiple,
+                    config.getWriteMaxTries());
+        } else {
+            // Should not happen! This method is not called in case configuration errors and writeType is validated
+            // already in initialization (validateAndParseWriteParameters).
+            // We keep this here for future-proofing the code (new writeType values)
+            throw new NotImplementedException(String.format(
+                    "writeType does not equal %s or %s and thus configuration is invalid. Should not end up this far with configuration error.",
+                    WRITE_TYPE_COIL, WRITE_TYPE_HOLDING));
+        }
+        return request;
+    }
+
+    private void processJsonTransform(Command command, String transformOutput) {
+        ModbusCommunicationInterface localComms = this.comms;
+        if (localComms == null) {
+            return;
+        }
+        Collection<ModbusWriteRequestBlueprint> requests;
+        try {
+            requests = WriteRequestJsonUtilities.fromJson(slaveId, transformOutput);
+        } catch (IllegalArgumentException | IllegalStateException e) {
+            logger.warn(
+                    "Thing {} '{}' could handle transformation result '{}'. Original command {}. Error details follow",
+                    getThing().getUID(), getThing().getLabel(), transformOutput, command, e);
+            return;
+        }
+
+        requests.stream().forEach(request -> {
+            logger.trace("Submitting write request: {} to endpoint {} (based from transformation {})", request,
+                    localComms.getEndpoint(), transformOutput);
+            localComms.submitOneTimeWrite(request, this::onWriteResponse, this::handleWriteError);
+        });
+    }
+
+    @Override
+    public synchronized void initialize() {
+        // Initialize the thing. If done set status to ONLINE to indicate proper working.
+        // Long running initialization should be done asynchronously in background.
+        try {
+            logger.trace("initialize() of thing {} '{}' starting", thing.getUID(), thing.getLabel());
+            ModbusDataConfiguration localConfig = config = getConfigAs(ModbusDataConfiguration.class);
+            updateUnchangedValuesEveryMillis = localConfig.getUpdateUnchangedValuesEveryMillis();
+            Bridge bridge = getBridge();
+            if (bridge == null || !bridge.getStatus().equals(ThingStatus.ONLINE)) {
+                logger.debug("Thing {} '{}' has no bridge or it is not online", getThing().getUID(),
+                        getThing().getLabel());
+                updateStatusIfChanged(ThingStatus.OFFLINE, ThingStatusDetail.BRIDGE_OFFLINE, "No online bridge");
+                return;
+            }
+            BridgeHandler bridgeHandler = bridge.getHandler();
+            if (bridgeHandler == null) {
+                logger.warn("Bridge {} '{}' has no handler.", bridge.getUID(), bridge.getLabel());
+                String errmsg = String.format("Bridge %s '%s' configuration incomplete or with errors", bridge.getUID(),
+                        bridge.getLabel());
+                throw new ModbusConfigurationException(errmsg);
+            }
+            if (bridgeHandler instanceof ModbusEndpointThingHandler) {
+                // Write-only thing, parent is endpoint
+                ModbusEndpointThingHandler endpointHandler = (ModbusEndpointThingHandler) bridgeHandler;
+                slaveId = endpointHandler.getSlaveId();
+                comms = endpointHandler.getCommunicationInterface();
+                childOfEndpoint = true;
+                functionCode = null;
+                readRequest = null;
+            } else {
+                ModbusPollerThingHandler localPollerHandler = (ModbusPollerThingHandler) bridgeHandler;
+                pollerHandler = localPollerHandler;
+                ModbusReadRequestBlueprint localReadRequest = localPollerHandler.getRequest();
+                if (localReadRequest == null) {
+                    logger.debug(
+                            "Poller {} '{}' has no read request -- configuration is changing or bridge having invalid configuration?",
+                            bridge.getUID(), bridge.getLabel());
+                    updateStatusIfChanged(ThingStatus.OFFLINE, ThingStatusDetail.BRIDGE_OFFLINE,
+                            String.format("Poller %s '%s' has no poll task", bridge.getUID(), bridge.getLabel()));
+                    return;
+                }
+                readRequest = localReadRequest;
+                slaveId = localReadRequest.getUnitID();
+                functionCode = localReadRequest.getFunctionCode();
+                comms = localPollerHandler.getCommunicationInterface();
+                pollStart = localReadRequest.getReference();
+                childOfEndpoint = false;
+            }
+            validateAndParseReadParameters(localConfig);
+            validateAndParseWriteParameters(localConfig);
+            validateMustReadOrWrite();
+
+            updateStatusIfChanged(ThingStatus.ONLINE);
+        } catch (ModbusConfigurationException | EndpointNotInitializedException e) {
+            logger.debug("Thing {} '{}' initialization error: {}", getThing().getUID(), getThing().getLabel(),
+                    e.getMessage());
+            updateStatusIfChanged(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR, e.getMessage());
+        } finally {
+            logger.trace("initialize() of thing {} '{}' finished", thing.getUID(), thing.getLabel());
+        }
+    }
+
+    @Override
+    public synchronized void dispose() {
+        config = null;
+        readValueType = null;
+        writeValueType = null;
+        readTransformation = null;
+        writeTransformation = null;
+        readIndex = Optional.empty();
+        readSubIndex = Optional.empty();
+        writeStart = null;
+        pollStart = 0;
+        slaveId = 0;
+        comms = null;
+        functionCode = null;
+        readRequest = null;
+        isWriteEnabled = false;
+        isReadEnabled = false;
+        writeParametersHavingTransformationOnly = false;
+        childOfEndpoint = false;
+        pollerHandler = null;
+        channelCache = new HashMap<>();
+        lastStatusInfoUpdate = LocalDateTime.MIN;
+        statusInfo = new ThingStatusInfo(ThingStatus.UNKNOWN, ThingStatusDetail.NONE, null);
+        channelLastUpdated = new HashMap<>(NUMER_OF_CHANNELS_HINT);
+        channelLastState = new HashMap<>(NUMER_OF_CHANNELS_HINT);
+    }
+
+    @Override
+    public synchronized void bridgeStatusChanged(ThingStatusInfo bridgeStatusInfo) {
+        logger.debug("bridgeStatusChanged for {}. Reseting handler", this.getThing().getUID());
+        this.dispose();
+        this.initialize();
+    }
+
+    private boolean hasConfigurationError() {
+        ThingStatusInfo statusInfo = getThing().getStatusInfo();
+        return statusInfo.getStatus() == ThingStatus.OFFLINE
+                && statusInfo.getStatusDetail() == ThingStatusDetail.CONFIGURATION_ERROR;
+    }
+
+    private void validateMustReadOrWrite() throws ModbusConfigurationException {
+        if (!isReadEnabled && !isWriteEnabled) {
+            throw new ModbusConfigurationException("Should try to read or write data!");
+        }
+    }
+
+    private void validateAndParseReadParameters(ModbusDataConfiguration config) throws ModbusConfigurationException {
+        ModbusReadFunctionCode functionCode = this.functionCode;
+        boolean readingDiscreteOrCoil = functionCode == ModbusReadFunctionCode.READ_COILS
+                || functionCode == ModbusReadFunctionCode.READ_INPUT_DISCRETES;
+        boolean readStartMissing = StringUtils.isBlank(config.getReadStart());
+        boolean readValueTypeMissing = StringUtils.isBlank(config.getReadValueType());
+
+        if (childOfEndpoint && readRequest == null) {
+            if (!readStartMissing || !readValueTypeMissing) {
+                String errmsg = String.format(
+                        "Thing %s readStart=%s, and readValueType=%s were specified even though the data thing is child of endpoint (that is, write-only)!",
+                        getThing().getUID(), config.getReadStart(), config.getReadValueType());
+                throw new ModbusConfigurationException(errmsg);
+            }
+        }
+
+        // we assume readValueType=bit by default if it is missing
+        boolean allMissingOrAllPresent = (readStartMissing && readValueTypeMissing)
+                || (!readStartMissing && (!readValueTypeMissing || readingDiscreteOrCoil));
+        if (!allMissingOrAllPresent) {
+            String errmsg = String.format(
+                    "Thing %s readStart=%s, and readValueType=%s should be all present or all missing!",
+                    getThing().getUID(), config.getReadStart(), config.getReadValueType());
+            throw new ModbusConfigurationException(errmsg);
+        } else if (!readStartMissing) {
+            // all read values are present
+            isReadEnabled = true;
+            if (readingDiscreteOrCoil && readValueTypeMissing) {
+                readValueType = ModbusConstants.ValueType.BIT;
+            } else {
+                try {
+                    readValueType = ValueType.fromConfigValue(config.getReadValueType());
+                } catch (IllegalArgumentException e) {
+                    String errmsg = String.format("Thing %s readValueType=%s is invalid!", getThing().getUID(),
+                            config.getReadValueType());
+                    throw new ModbusConfigurationException(errmsg);
+                }
+            }
+
+            if (readingDiscreteOrCoil && !ModbusConstants.ValueType.BIT.equals(readValueType)) {
+                String errmsg = String.format(
+                        "Thing %s invalid readValueType: Only readValueType='%s' (or undefined) supported with coils or discrete inputs. Value type was: %s",
+                        getThing().getUID(), ModbusConstants.ValueType.BIT, config.getReadValueType());
+                throw new ModbusConfigurationException(errmsg);
+            }
+        } else {
+            isReadEnabled = false;
+        }
+
+        if (isReadEnabled) {
+            String readStart = config.getReadStart();
+            if (readStart == null) {
+                throw new ModbusConfigurationException(
+                        String.format("Thing %s invalid readStart: %s", getThing().getUID(), config.getReadStart()));
+            }
+            String[] readParts = readStart.split("\\.", 2);
+            try {
+                readIndex = Optional.of(Integer.parseInt(readParts[0]));
+                if (readParts.length == 2) {
+                    readSubIndex = Optional.of(Integer.parseInt(readParts[1]));
+                } else {
+                    readSubIndex = Optional.empty();
+                }
+            } catch (IllegalArgumentException e) {
+                String errmsg = String.format("Thing %s invalid readStart: %s", getThing().getUID(),
+                        config.getReadStart());
+                throw new ModbusConfigurationException(errmsg);
+            }
+        }
+        readTransformation = new Transformation(config.getReadTransform());
+        validateReadIndex();
+    }
+
+    private void validateAndParseWriteParameters(ModbusDataConfiguration config) throws ModbusConfigurationException {
+        boolean writeTypeMissing = StringUtils.isBlank(config.getWriteType());
+        boolean writeStartMissing = StringUtils.isBlank(config.getWriteStart());
+        boolean writeValueTypeMissing = StringUtils.isBlank(config.getWriteValueType());
+        boolean writeTransformationMissing = StringUtils.isBlank(config.getWriteTransform());
+        writeTransformation = new Transformation(config.getWriteTransform());
+        boolean writingCoil = WRITE_TYPE_COIL.equals(config.getWriteType());
+        writeParametersHavingTransformationOnly = (writeTypeMissing && writeStartMissing && writeValueTypeMissing
+                && !writeTransformationMissing);
+        boolean allMissingOrAllPresentOrOnlyNonDefaultTransform = //
+                // read-only thing, no write specified
+                (writeTypeMissing && writeStartMissing && writeValueTypeMissing)
+                        // mandatory write parameters provided. With coils one can drop value type
+                        || (!writeTypeMissing && !writeStartMissing && (!writeValueTypeMissing || writingCoil))
+                        // only transformation provided
+                        || writeParametersHavingTransformationOnly;
+        if (!allMissingOrAllPresentOrOnlyNonDefaultTransform) {
+            String errmsg = String.format(
+                    "writeType=%s, writeStart=%s, and writeValueType=%s should be all present, or all missing! Alternatively, you can provide just writeTransformation, and use transformation returning JSON.",
+                    config.getWriteType(), config.getWriteStart(), config.getWriteValueType());
+            throw new ModbusConfigurationException(errmsg);
+        } else if (!writeTypeMissing || writeParametersHavingTransformationOnly) {
+            isWriteEnabled = true;
+            // all write values are present
+            if (!writeParametersHavingTransformationOnly && !WRITE_TYPE_HOLDING.equals(config.getWriteType())
+                    && !WRITE_TYPE_COIL.equals(config.getWriteType())) {
+                String errmsg = String.format("Invalid writeType=%s. Expecting %s or %s!", config.getWriteType(),
+                        WRITE_TYPE_HOLDING, WRITE_TYPE_COIL);
+                throw new ModbusConfigurationException(errmsg);
+            }
+            final ValueType localWriteValueType;
+            if (writeParametersHavingTransformationOnly) {
+                // Placeholder for further checks
+                localWriteValueType = writeValueType = ModbusConstants.ValueType.INT16;
+            } else if (writingCoil && writeValueTypeMissing) {
+                localWriteValueType = writeValueType = ModbusConstants.ValueType.BIT;
+            } else {
+                try {
+                    localWriteValueType = writeValueType = ValueType.fromConfigValue(config.getWriteValueType());
+                } catch (IllegalArgumentException e) {
+                    String errmsg = String.format("Invalid writeValueType=%s!", config.getWriteValueType());
+                    throw new ModbusConfigurationException(errmsg);
+                }
+            }
+
+            if (writingCoil && !ModbusConstants.ValueType.BIT.equals(localWriteValueType)) {
+                String errmsg = String.format(
+                        "Invalid writeValueType: Only writeValueType='%s' (or undefined) supported with coils. Value type was: %s",
+                        ModbusConstants.ValueType.BIT, config.getWriteValueType());
+                throw new ModbusConfigurationException(errmsg);
+            } else if (!writingCoil && localWriteValueType.getBits() < 16) {
+                // trying to write holding registers with < 16 bit value types. Not supported
+                String errmsg = String.format(
+                        "Invalid writeValueType: Only writeValueType with larger or equal to 16 bits are supported holding registers. Value type was: %s",
+                        config.getWriteValueType());
+                throw new ModbusConfigurationException(errmsg);
+            }
+
+            try {
+                if (!writeParametersHavingTransformationOnly) {
+                    String localWriteStart = config.getWriteStart();
+                    if (localWriteStart == null) {
+                        String errmsg = String.format("Thing %s invalid writeStart: %s", getThing().getUID(),
+                                config.getWriteStart());
+                        throw new ModbusConfigurationException(errmsg);
+                    }
+                    writeStart = Integer.parseInt(localWriteStart.trim());
+                }
+            } catch (IllegalArgumentException e) {
+                String errmsg = String.format("Thing %s invalid writeStart: %s", getThing().getUID(),
+                        config.getWriteStart());
+                throw new ModbusConfigurationException(errmsg);
+            }
+        } else {
+            isWriteEnabled = false;
+        }
+    }
+
+    private void validateReadIndex() throws ModbusConfigurationException {
+        @Nullable
+        ModbusReadRequestBlueprint readRequest = this.readRequest;
+        ValueType readValueType = this.readValueType;
+        if (!readIndex.isPresent() || readRequest == null) {
+            return;
+        }
+        assert readValueType != null;
+        // bits represented by the value type, e.g. int32 -> 32
+        int valueTypeBitCount = readValueType.getBits();
+        int dataElementBits;
+        switch (readRequest.getFunctionCode()) {
+            case READ_INPUT_REGISTERS:
+            case READ_MULTIPLE_REGISTERS:
+                dataElementBits = 16;
+                break;
+            case READ_COILS:
+            case READ_INPUT_DISCRETES:
+                dataElementBits = 1;
+                break;
+            default:
+                throw new IllegalStateException(readRequest.getFunctionCode().toString());
+        }
+
+        boolean bitQuery = dataElementBits == 1;
+        if (bitQuery && readSubIndex.isPresent()) {
+            String errmsg = String.format("readStart=X.Y is not allowed to be used with coils or discrete inputs!");
+            throw new ModbusConfigurationException(errmsg);
+        }
+
+        if (valueTypeBitCount >= 16 && readSubIndex.isPresent()) {
+            String errmsg = String
+                    .format("readStart=X.Y is not allowed to be used with value types larger than 16bit!");
+            throw new ModbusConfigurationException(errmsg);
+        } else if (!bitQuery && valueTypeBitCount < 16 && !readSubIndex.isPresent()) {
+            String errmsg = String.format("readStart=X.Y must be used with value types less than 16bit!");
+            throw new ModbusConfigurationException(errmsg);
+        } else if (readSubIndex.isPresent() && (readSubIndex.get() + 1) * valueTypeBitCount > 16) {
+            // the sub index Y (in X.Y) is above the register limits
+            String errmsg = String.format("readStart=X.Y, the value Y is too large");
+            throw new ModbusConfigurationException(errmsg);
+        }
+
+        // Determine bit positions polled, both start and end inclusive
+        int pollStartBitIndex = readRequest.getReference() * dataElementBits;
+        int pollEndBitIndex = pollStartBitIndex + readRequest.getDataLength() * dataElementBits - 1;
+
+        // Determine bit positions read, both start and end inclusive
+        int readStartBitIndex = readIndex.get() * dataElementBits + readSubIndex.orElse(0) * valueTypeBitCount;
+        int readEndBitIndex = readStartBitIndex + valueTypeBitCount - 1;
+
+        if (readStartBitIndex < pollStartBitIndex || readEndBitIndex > pollEndBitIndex) {
+            String errmsg = String.format(
+                    "Out-of-bounds: Poller is reading from index %d to %d (inclusive) but this thing configured to read '%s' starting from element %d. Exceeds polled data bounds.",
+                    pollStartBitIndex / dataElementBits, pollEndBitIndex / dataElementBits, readValueType,
+                    readIndex.get());
+            throw new ModbusConfigurationException(errmsg);
+        }
+    }
+
+    private boolean containsOnOff(List<Class<? extends State>> channelAcceptedDataTypes) {
+        return channelAcceptedDataTypes.stream().anyMatch(clz -> {
+            return clz.equals(OnOffType.class);
+        });
+    }
+
+    private boolean containsOpenClosed(List<Class<? extends State>> acceptedDataTypes) {
+        return acceptedDataTypes.stream().anyMatch(clz -> {
+            return clz.equals(OpenClosedType.class);
+        });
+    }
+
+    public synchronized void onReadResult(AsyncModbusReadResult result) {
+        result.getRegisters().ifPresent(registers -> onRegisters(result.getRequest(), registers));
+        result.getBits().ifPresent(bits -> onBits(result.getRequest(), bits));
+    }
+
+    public synchronized void handleReadError(AsyncModbusFailure<ModbusReadRequestBlueprint> failure) {
+        onError(failure.getRequest(), failure.getCause());
+    }
+
+    public synchronized void handleWriteError(AsyncModbusFailure<ModbusWriteRequestBlueprint> failure) {
+        onError(failure.getRequest(), failure.getCause());
+    }
+
+    private synchronized void onRegisters(ModbusReadRequestBlueprint request, ModbusRegisterArray registers) {
+        if (hasConfigurationError()) {
+            return;
+        } else if (!isReadEnabled) {
+            return;
+        }
+        ValueType readValueType = this.readValueType;
+        if (readValueType == null) {
+            return;
+        }
+        State numericState;
+
+        // extractIndex:
+        // e.g. with bit, extractIndex=4 means 5th bit (from right) ("10.4" -> 5th bit of register 10, "10.4" -> 5th bit
+        // of register 10)
+        // bit of second register)
+        // e.g. with 8bit integer, extractIndex=3 means high byte of second register
+        //
+        // with <16 bit types, this is the index of the N'th 1-bit/8-bit item. Each register has 16/2 items,
+        // respectively.
+        // with >=16 bit types, this is index of first register
+        int extractIndex;
+        if (readValueType.getBits() >= 16) {
+            // Invariant, checked in initialize
+            assert readSubIndex.orElse(0) == 0;
+            extractIndex = readIndex.get() - pollStart;
+        } else {
+            int subIndex = readSubIndex.orElse(0);
+            int itemsPerRegister = 16 / readValueType.getBits();
+            extractIndex = (readIndex.get() - pollStart) * itemsPerRegister + subIndex;
+        }
+        numericState = ModbusBitUtilities.extractStateFromRegisters(registers, extractIndex, readValueType)
+                .map(state -> (State) state).orElse(UnDefType.UNDEF);
+        boolean boolValue = !numericState.equals(DecimalType.ZERO);
+        Map<ChannelUID, State> values = processUpdatedValue(numericState, boolValue);
+        logger.debug(
+                "Thing {} channels updated: {}. readValueType={}, readIndex={}, readSubIndex(or 0)={}, extractIndex={} -> numeric value {} and boolValue={}. Registers {} for request {}",
+                thing.getUID(), values, readValueType, readIndex, readSubIndex.orElse(0), extractIndex, numericState,
+                boolValue, registers, request);
+    }
+
+    private synchronized void onBits(ModbusReadRequestBlueprint request, BitArray bits) {
+        if (hasConfigurationError()) {
+            return;
+        } else if (!isReadEnabled) {
+            return;
+        }
+        boolean boolValue = bits.getBit(readIndex.get() - pollStart);
+        DecimalType numericState = boolValue ? new DecimalType(BigDecimal.ONE) : DecimalType.ZERO;
+        Map<ChannelUID, State> values = processUpdatedValue(numericState, boolValue);
+        logger.debug(
+                "Thing {} channels updated: {}. readValueType={}, readIndex={} -> numeric value {} and boolValue={}. Bits {} for request {}",
+                thing.getUID(), values, readValueType, readIndex, numericState, boolValue, bits, request);
+    }
+
+    private synchronized void onError(ModbusReadRequestBlueprint request, Exception error) {
+        if (hasConfigurationError()) {
+            return;
+        } else if (!isReadEnabled) {
+            return;
+        }
+        if (error instanceof ModbusConnectionException) {
+            logger.trace("Thing {} '{}' had {} error on read: {}", getThing().getUID(), getThing().getLabel(),
+                    error.getClass().getSimpleName(), error.toString());
+        } else if (error instanceof ModbusTransportException) {
+            logger.trace("Thing {} '{}' had {} error on read: {}", getThing().getUID(), getThing().getLabel(),
+                    error.getClass().getSimpleName(), error.toString());
+        } else {
+            logger.error(
+                    "Thing {} '{}' had {} error on read: {} (message: {}). Stack trace follows since this is unexpected error.",
+                    getThing().getUID(), getThing().getLabel(), error.getClass().getName(), error.toString(),
+                    error.getMessage(), error);
+        }
+        Map<ChannelUID, State> states = new HashMap<>();
+        ChannelUID lastReadErrorUID = getChannelUID(ModbusBindingConstantsInternal.CHANNEL_LAST_READ_ERROR);
+        if (isLinked(lastReadErrorUID)) {
+            states.put(lastReadErrorUID, new DateTimeType());
+        }
+
+        synchronized (this) {
+            // Update channels
+            states.forEach((uid, state) -> {
+                tryUpdateState(uid, state);
+            });
+
+            updateStatusIfChanged(ThingStatus.OFFLINE, ThingStatusDetail.COMMUNICATION_ERROR,
+                    String.format("Error (%s) with read. Request: %s. Description: %s. Message: %s",
+                            error.getClass().getSimpleName(), request, error.toString(), error.getMessage()));
+        }
+    }
+
+    private synchronized void onError(ModbusWriteRequestBlueprint request, Exception error) {
+        if (hasConfigurationError()) {
+            return;
+        } else if (!isWriteEnabled) {
+            return;
+        }
+        if (error instanceof ModbusConnectionException) {
+            logger.debug("Thing {} '{}' had {} error on write: {}", getThing().getUID(), getThing().getLabel(),
+                    error.getClass().getSimpleName(), error.toString());
+        } else if (error instanceof ModbusTransportException) {
+            logger.debug("Thing {} '{}' had {} error on write: {}", getThing().getUID(), getThing().getLabel(),
+                    error.getClass().getSimpleName(), error.toString());
+        } else {
+            logger.error(
+                    "Thing {} '{}' had {} error on write: {} (message: {}). Stack trace follows since this is unexpected error.",
+                    getThing().getUID(), getThing().getLabel(), error.getClass().getName(), error.toString(),
+                    error.getMessage(), error);
+        }
+        Map<ChannelUID, State> states = new HashMap<>();
+        ChannelUID lastWriteErrorUID = getChannelUID(ModbusBindingConstantsInternal.CHANNEL_LAST_WRITE_ERROR);
+        if (isLinked(lastWriteErrorUID)) {
+            states.put(lastWriteErrorUID, new DateTimeType());
+        }
+
+        synchronized (this) {
+            // Update channels
+            states.forEach((uid, state) -> {
+                tryUpdateState(uid, state);
+            });
+
+            updateStatusIfChanged(ThingStatus.OFFLINE, ThingStatusDetail.COMMUNICATION_ERROR,
+                    String.format("Error (%s) with write. Request: %s. Description: %s. Message: %s",
+                            error.getClass().getSimpleName(), request, error.toString(), error.getMessage()));
+        }
+    }
+
+    public synchronized void onWriteResponse(AsyncModbusWriteResult result) {
+        if (hasConfigurationError()) {
+            return;
+        } else if (!isWriteEnabled) {
+            return;
+        }
+        logger.debug("Successful write, matching request {}", result.getRequest());
+        updateStatusIfChanged(ThingStatus.ONLINE);
+        ChannelUID lastWriteSuccessUID = getChannelUID(ModbusBindingConstantsInternal.CHANNEL_LAST_WRITE_SUCCESS);
+        if (isLinked(lastWriteSuccessUID)) {
+            updateState(lastWriteSuccessUID, new DateTimeType());
+        }
+    }
+
+    /**
+     * Update linked channels
+     *
+     * @param numericState numeric state corresponding to polled data (or UNDEF with floating point NaN or infinity)
+     * @param boolValue boolean value corresponding to polled data
+     * @return updated channel data
+     */
+    private Map<ChannelUID, State> processUpdatedValue(State numericState, boolean boolValue) {
+        Transformation localReadTransformation = readTransformation;
+        if (localReadTransformation == null) {
+            // We should always have transformation available if thing is initalized properly
+            logger.trace("No transformation available, aborting processUpdatedValue");
+            return Collections.emptyMap();
+        }
+        Map<ChannelUID, State> states = new HashMap<>();
+        CHANNEL_ID_TO_ACCEPTED_TYPES.keySet().stream().forEach(channelId -> {
+            ChannelUID channelUID = getChannelUID(channelId);
+            if (!isLinked(channelUID)) {
+                return;
+            }
+            List<Class<? extends State>> acceptedDataTypes = CHANNEL_ID_TO_ACCEPTED_TYPES.get(channelId);
+            if (acceptedDataTypes.isEmpty()) {
+                return;
+            }
+
+            State boolLikeState;
+            if (containsOnOff(acceptedDataTypes)) {
+                boolLikeState = boolValue ? OnOffType.ON : OnOffType.OFF;
+            } else if (containsOpenClosed(acceptedDataTypes)) {
+                boolLikeState = boolValue ? OpenClosedType.OPEN : OpenClosedType.CLOSED;
+            } else {
+                boolLikeState = null;
+            }
+
+            State transformedState;
+            if (localReadTransformation.isIdentityTransform()) {
+                if (boolLikeState != null) {
+                    // A bit of smartness for ON/OFF and OPEN/CLOSED with boolean like items
+                    transformedState = boolLikeState;
+                } else {
+                    // Numeric states always go through transformation. This allows value of 17.5 to be
+                    // converted to
+                    // 17.5% with percent types (instead of raising error)
+                    transformedState = localReadTransformation.transformState(bundleContext, acceptedDataTypes,
+                            numericState);
+                }
+            } else {
+                transformedState = localReadTransformation.transformState(bundleContext, acceptedDataTypes,
+                        numericState);
+            }
+
+            if (transformedState != null) {
+                logger.trace(
+                        "Channel {} will be updated to '{}' (type {}). Input data: number value {} (value type '{}' taken into account) and bool value {}. Transformation: {}",
+                        channelId, transformedState, transformedState.getClass().getSimpleName(), numericState,
+                        readValueType, boolValue,
+                        localReadTransformation.isIdentityTransform() ? "<identity>" : localReadTransformation);
+                states.put(channelUID, transformedState);
+            } else {
+                String types = StringUtils.join(acceptedDataTypes.stream().map(cls -> cls.getSimpleName()).toArray(),
+                        ", ");
+                logger.warn(
+                        "Channel {} will not be updated since transformation was unsuccessful. Channel is expecting the following data types [{}]. Input data: number value {} (value type '{}' taken into account) and bool value {}. Transformation: {}",
+                        channelId, types, numericState, readValueType, boolValue,
+                        localReadTransformation.isIdentityTransform() ? "<identity>" : localReadTransformation);
+            }
+        });
+
+        ChannelUID lastReadSuccessUID = getChannelUID(ModbusBindingConstantsInternal.CHANNEL_LAST_READ_SUCCESS);
+        if (isLinked(lastReadSuccessUID)) {
+            states.put(lastReadSuccessUID, new DateTimeType());
+        }
+        updateExpiredChannels(states);
+        return states;
+    }
+
+    private void updateExpiredChannels(Map<ChannelUID, State> states) {
+        synchronized (this) {
+            updateStatusIfChanged(ThingStatus.ONLINE);
+            long now = System.currentTimeMillis();
+            // Update channels that have not been updated in a while, or when their values has changed
+            states.forEach((uid, state) -> updateExpiredChannel(now, uid, state));
+            channelLastState = states;
+        }
+    }
+
+    // since lastState can be null, and "lastState == null" in conditional is not useless
+    @SuppressWarnings("null")
+    private void updateExpiredChannel(long now, ChannelUID uid, State state) {
+        @Nullable
+        State lastState = channelLastState.get(uid);
+        long lastUpdatedMillis = channelLastUpdated.getOrDefault(uid, 0L);
+        long millisSinceLastUpdate = now - lastUpdatedMillis;
+        if (lastUpdatedMillis <= 0L || lastState == null || updateUnchangedValuesEveryMillis <= 0L
+                || millisSinceLastUpdate > updateUnchangedValuesEveryMillis || !lastState.equals(state)) {
+            tryUpdateState(uid, state);
+            channelLastUpdated.put(uid, now);
+        }
+    }
+
+    private void tryUpdateState(ChannelUID uid, State state) {
+        try {
+            updateState(uid, state);
+        } catch (IllegalArgumentException e) {
+            logger.warn("Error updating state '{}' (type {}) to channel {}: {} {}", state,
+                    Optional.ofNullable(state).map(s -> s.getClass().getName()).orElse("null"), uid,
+                    e.getClass().getName(), e.getMessage());
+        }
+    }
+
+    private ChannelUID getChannelUID(String channelID) {
+        return channelCache.computeIfAbsent(channelID, id -> new ChannelUID(getThing().getUID(), id));
+    }
+
+    private void updateStatusIfChanged(ThingStatus status) {
+        updateStatusIfChanged(status, ThingStatusDetail.NONE, null);
+    }
+
+    private void updateStatusIfChanged(ThingStatus status, ThingStatusDetail statusDetail,
+            @Nullable String description) {
+        ThingStatusInfo newStatusInfo = new ThingStatusInfo(status, statusDetail, description);
+        Duration durationSinceLastUpdate = Duration.between(lastStatusInfoUpdate, LocalDateTime.now());
+        boolean intervalElapsed = MIN_STATUS_INFO_UPDATE_INTERVAL.minus(durationSinceLastUpdate).isNegative();
+        if (statusInfo.getStatus() == ThingStatus.UNKNOWN || !statusInfo.equals(newStatusInfo) || intervalElapsed) {
+            statusInfo = newStatusInfo;
+            lastStatusInfoUpdate = LocalDateTime.now();
+            updateStatus(newStatusInfo);
+        }
+    }
+
+    /**
+     * Update status using pre-constructed ThingStatusInfo
+     *
+     * Implementation adapted from BaseThingHandler updateStatus implementations
+     *
+     * @param statusInfo new status info
+     */
+    protected void updateStatus(ThingStatusInfo statusInfo) {
+        synchronized (this) {
+            ThingHandlerCallback callback = getCallback();
+            if (callback != null) {
+                callback.statusUpdated(this.thing, statusInfo);
+            } else {
+                logger.warn("Handler {} tried updating the thing status although the handler was already disposed.",
+                        this.getClass().getSimpleName());
+            }
+        }
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/handler/ModbusSerialThingHandler.java

@@ -0,0 +1,115 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal.handler;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Optional;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.binding.modbus.discovery.internal.ModbusEndpointDiscoveryService;
+import org.openhab.binding.modbus.handler.EndpointNotInitializedException;
+import org.openhab.binding.modbus.internal.ModbusConfigurationException;
+import org.openhab.binding.modbus.internal.config.ModbusSerialConfiguration;
+import org.openhab.core.thing.Bridge;
+import org.openhab.core.thing.ThingUID;
+import org.openhab.core.thing.binding.ThingHandlerService;
+import org.openhab.io.transport.modbus.ModbusManager;
+import org.openhab.io.transport.modbus.endpoint.EndpointPoolConfiguration;
+import org.openhab.io.transport.modbus.endpoint.ModbusSerialSlaveEndpoint;
+
+/**
+ * Endpoint thing handler for serial slaves
+ *
+ * @author Sami Salonen - Initial contribution
+ */
+@NonNullByDefault
+public class ModbusSerialThingHandler
+        extends AbstractModbusEndpointThingHandler<ModbusSerialSlaveEndpoint, ModbusSerialConfiguration> {
+
+    public ModbusSerialThingHandler(Bridge bridge, ModbusManager manager) {
+        super(bridge, manager);
+    }
+
+    @Override
+    protected void configure() throws ModbusConfigurationException {
+        ModbusSerialConfiguration config = getConfigAs(ModbusSerialConfiguration.class);
+        String port = config.getPort();
+        int baud = config.getBaud();
+        String flowControlIn = config.getFlowControlIn();
+        String flowControlOut = config.getFlowControlOut();
+        String stopBits = config.getStopBits();
+        String parity = config.getParity();
+        String encoding = config.getEncoding();
+        if (port == null || flowControlIn == null || flowControlOut == null || stopBits == null || parity == null
+                || encoding == null) {
+            throw new ModbusConfigurationException(
+                    "port, baud, flowControlIn, flowControlOut, stopBits, parity, encoding all must be non-null!");
+        }
+
+        this.config = config;
+
+        EndpointPoolConfiguration poolConfiguration = new EndpointPoolConfiguration();
+        this.poolConfiguration = poolConfiguration;
+        poolConfiguration.setConnectMaxTries(config.getConnectMaxTries());
+        poolConfiguration.setConnectTimeoutMillis(config.getConnectTimeoutMillis());
+        poolConfiguration.setInterTransactionDelayMillis(config.getTimeBetweenTransactionsMillis());
+
+        // Never reconnect serial connections "automatically"
+        poolConfiguration.setInterConnectDelayMillis(1000);
+        poolConfiguration.setReconnectAfterMillis(-1);
+
+        endpoint = new ModbusSerialSlaveEndpoint(port, baud, flowControlIn, flowControlOut, config.getDataBits(),
+                stopBits, parity, encoding, config.isEcho(), config.getReceiveTimeoutMillis());
+    }
+
+    /**
+     * Return true if auto discovery is enabled in the config
+     */
+    @Override
+    public boolean isDiscoveryEnabled() {
+        if (config != null) {
+            return config.isDiscoveryEnabled();
+        } else {
+            return false;
+        }
+    }
+
+    @SuppressWarnings("null") // Since endpoint in Optional.map cannot be null
+    @Override
+    protected String formatConflictingParameterError() {
+        return String.format(
+                "Endpoint '%s' has conflicting parameters: parameters of this thing (%s '%s') are different from some other thing's parameter. Ensure that all endpoints pointing to serial port '%s' have same parameters.",
+                endpoint, thing.getUID(), this.thing.getLabel(),
+                Optional.ofNullable(this.endpoint).map(e -> e.getPortName()).orElse("<null>"));
+    }
+
+    @Override
+    public int getSlaveId() throws EndpointNotInitializedException {
+        ModbusSerialConfiguration config = this.config;
+        if (config == null) {
+            throw new EndpointNotInitializedException();
+        }
+        return config.getId();
+    }
+
+    @Override
+    public ThingUID getUID() {
+        return getThing().getUID();
+    }
+
+    @Override
+    public Collection<Class<? extends ThingHandlerService>> getServices() {
+        return Collections.singleton(ModbusEndpointDiscoveryService.class);
+    }
+}

bundles/org.openhab.binding.modbus/src/main/java/org/openhab/binding/modbus/internal/handler/ModbusTcpThingHandler.java

@@ -0,0 +1,105 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal.handler;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Optional;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.binding.modbus.discovery.internal.ModbusEndpointDiscoveryService;
+import org.openhab.binding.modbus.handler.EndpointNotInitializedException;
+import org.openhab.binding.modbus.internal.ModbusConfigurationException;
+import org.openhab.binding.modbus.internal.config.ModbusTcpConfiguration;
+import org.openhab.core.thing.Bridge;
+import org.openhab.core.thing.ThingUID;
+import org.openhab.core.thing.binding.ThingHandlerService;
+import org.openhab.io.transport.modbus.ModbusManager;
+import org.openhab.io.transport.modbus.endpoint.EndpointPoolConfiguration;
+import org.openhab.io.transport.modbus.endpoint.ModbusTCPSlaveEndpoint;
+
+/**
+ * Endpoint thing handler for TCP slaves
+ *
+ * @author Sami Salonen - Initial contribution
+ */
+@NonNullByDefault
+public class ModbusTcpThingHandler
+        extends AbstractModbusEndpointThingHandler<ModbusTCPSlaveEndpoint, ModbusTcpConfiguration> {
+
+    public ModbusTcpThingHandler(Bridge bridge, ModbusManager manager) {
+        super(bridge, manager);
+    }
+
+    @Override
+    protected void configure() throws ModbusConfigurationException {
+        ModbusTcpConfiguration config = getConfigAs(ModbusTcpConfiguration.class);
+
+        String host = config.getHost();
+        if (host == null) {
+            throw new ModbusConfigurationException("host must be non-null!");
+        }
+
+        this.config = config;
+        endpoint = new ModbusTCPSlaveEndpoint(host, config.getPort());
+
+        EndpointPoolConfiguration poolConfiguration = new EndpointPoolConfiguration();
+        this.poolConfiguration = poolConfiguration;
+        poolConfiguration.setConnectMaxTries(config.getConnectMaxTries());
+        poolConfiguration.setConnectTimeoutMillis(config.getConnectTimeoutMillis());
+        poolConfiguration.setInterConnectDelayMillis(config.getTimeBetweenReconnectMillis());
+        poolConfiguration.setInterTransactionDelayMillis(config.getTimeBetweenTransactionsMillis());
+        poolConfiguration.setReconnectAfterMillis(config.getReconnectAfterMillis());
+    }
+
+    @SuppressWarnings("null") // since Optional.map is always called with NonNull argument
+    @Override
+    protected String formatConflictingParameterError() {
+        return String.format(
+                "Endpoint '%s' has conflicting parameters: parameters of this thing (%s '%s') are different from some other thing's parameter. Ensure that all endpoints pointing to tcp slave '%s:%s' have same parameters.",
+                endpoint, thing.getUID(), this.thing.getLabel(),
+                Optional.ofNullable(this.endpoint).map(e -> e.getAddress()).orElse("<null>"),
+                Optional.ofNullable(this.endpoint).map(e -> String.valueOf(e.getPort())).orElse("<null>"));
+    }
+
+    @Override
+    public int getSlaveId() throws EndpointNotInitializedException {
+        ModbusTcpConfiguration localConfig = config;
+        if (localConfig == null) {
+            throw new EndpointNotInitializedException();
+        }
+        return localConfig.getId();
+    }
+
+    @Override
+    public ThingUID getUID() {
+        return getThing().getUID();
+    }
+
+    /**
+     * Returns true if discovery is enabled
+     */
+    @Override
+    public boolean isDiscoveryEnabled() {
+        if (config != null) {
+            return config.isDiscoveryEnabled();
+        } else {
+            return false;
+        }
+    }
+
+    @Override
+    public Collection<Class<? extends ThingHandlerService>> getServices() {
+        return Collections.singleton(ModbusEndpointDiscoveryService.class);
+    }
+}

bundles/org.openhab.binding.modbus/src/main/resources/OH-INF/binding/binding.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<binding:binding id="modbus" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:binding="https://openhab.org/schemas/binding/v1.0.0"
+	xsi:schemaLocation="https://openhab.org/schemas/binding/v1.0.0 https://openhab.org/schemas/binding-1.0.0.xsd">
+	<name>Modbus Binding</name>
+	<description>Binding for Modbus</description>
+	<author>Sami Salonen</author>
+
+</binding:binding>

bundles/org.openhab.binding.modbus/src/main/resources/OH-INF/thing/bridge-poller.xml

@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<thing:thing-descriptions bindingId="modbus"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:thing="https://openhab.org/schemas/thing-description/v1.0.0"
+	xsi:schemaLocation="https://openhab.org/schemas/thing-description/v1.0.0 https://openhab.org/schemas/thing-description-1.0.0.xsd">
+	<bridge-type id="poller">
+		<supported-bridge-type-refs>
+			<bridge-type-ref id="tcp"/>
+			<bridge-type-ref id="serial"/>
+		</supported-bridge-type-refs>
+
+		<label>Regular Poll</label>
+		<description>Regular poll of data from Modbus slaves</description>
+		<config-description>
+			<parameter name="refresh" type="integer" min="0" unit="ms">
+				<label>Poll Interval</label>
+				<description>Poll interval in milliseconds. Use zero to disable automatic polling.</description>
+				<default>500</default>
+			</parameter>
+			<parameter name="start" type="integer">
+				<label>Start</label>
+				<description><![CDATA[Address of the first register, coil, or discrete input to poll.
+				<br />
+				<br />Input as zero-based index number, e.g. in place of 400001 (first holding register), use the address 0.]]></description>
+				<default>0</default>
+			</parameter>
+			<parameter name="length" type="integer" required="true">
+				<label>Length</label>
+				<description><![CDATA[Number of registers, coils or discrete inputs to read.
+				<br />
+				<br />Maximum number of registers is 125 while 2000 is maximum for coils and discrete inputs.]]></description>
+			</parameter>
+			<parameter name="type" type="text" required="true">
+				<label>Type</label>
+				<description>Type of modbus items to poll</description>
+				<options>
+					<option value="coil">coil, or digital out (DO)</option>
+					<option value="discrete">discrete input, or digital in (DI)</option>
+					<option value="holding">holding register</option>
+					<option value="input">input register</option>
+				</options>
+			</parameter>
+			<parameter name="maxTries" type="integer" min="1">
+				<label>Maximum Tries When Reading</label>
+				<default>3</default>
+				<description>Number of tries when reading data, if some of the reading fail. For single try, enter 1.</description>
+			</parameter>
+			<parameter name="cacheMillis" type="integer" min="0" unit="ms">
+				<label>Cache Duration</label>
+				<default>50</default>
+				<description><![CDATA[Duration for data cache to be valid, in milliseconds. This cache is used only to serve REFRESH commands.
+					<br />
+					<br />Use zero to disable the caching.]]></description>
+				<advanced>true</advanced>
+			</parameter>
+		</config-description>
+	</bridge-type>
+</thing:thing-descriptions>

bundles/org.openhab.binding.modbus/src/main/resources/OH-INF/thing/bridge-serial.xml

@@ -0,0 +1,148 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<thing:thing-descriptions bindingId="modbus"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:thing="https://openhab.org/schemas/thing-description/v1.0.0"
+	xsi:schemaLocation="https://openhab.org/schemas/thing-description/v1.0.0 https://openhab.org/schemas/thing-description-1.0.0.xsd">
+	<bridge-type id="serial">
+		<label>Modbus Serial Slave</label>
+		<description>Endpoint for Modbus serial slaves</description>
+		<config-description>
+			<parameter name="port" type="text" required="true">
+				<label>Serial Port</label>
+				<context>serial-port</context>
+				<limitToOptions>false</limitToOptions>
+				<description>Serial port to use, for example /dev/ttyS0 or COM1</description>
+			</parameter>
+
+			<parameter name="id" type="integer">
+				<label>Id</label>
+				<description>Slave id. Also known as station address or unit identifier.</description>
+				<default>1</default>
+			</parameter>
+
+			<!-- serial parameters -->
+			<parameter name="baud" type="integer" multiple="false">
+				<label>Baud</label>
+				<description>Baud of the connection</description>
+				<default>9600</default>
+				<options>
+					<option value="75">75</option>
+					<option value="110">110</option>
+					<option value="300">300</option>
+					<option value="1200">1200</option>
+					<option value="2400">2400</option>
+					<option value="4800">4800</option>
+					<option value="9600">9600</option>
+					<option value="19200">19200</option>
+					<option value="38400">38400</option>
+					<option value="57600">57600</option>
+					<option value="115200">115200</option>
+				</options>
+			</parameter>
+			<parameter name="stopBits" type="text" multiple="false">
+				<label>Stop Bits</label>
+				<description>Stop bits</description>
+				<default>1.0</default>
+				<options>
+					<option value="1.0">1</option>
+					<option value="1.5">1.5</option>
+					<option value="2.0">2</option>
+				</options>
+			</parameter>
+			<parameter name="parity" type="text" multiple="false">
+				<label>Parity</label>
+				<description>Parity</description>
+				<default>none</default>
+				<options>
+					<option value="none">None</option>
+					<option value="even">Even</option>
+					<option value="odd">Odd</option>
+				</options>
+			</parameter>
+			<parameter name="dataBits" type="integer" multiple="false">
+				<label>Data Bits</label>
+				<description>Data bits</description>
+				<default>8</default>
+				<options>
+					<option value="5">5</option>
+					<option value="6">6</option>
+					<option value="7">7</option>
+					<option value="8">8</option>
+				</options>
+			</parameter>
+			<parameter name="encoding" type="text" multiple="false">
+				<label>Encoding</label>
+				<description>Encoding</description>
+				<default>rtu</default>
+				<options>
+					<option value="ascii">ASCII</option>
+					<option value="rtu">RTU</option>
+					<option value="bin">BIN</option>
+				</options>
+			</parameter>
+			<parameter name="enableDiscovery" type="boolean">
+				<label>Discovery Enabled</label>
+				<description>When enabled we try to find a device specific handler. Turn this on if you're using one of the
+					supported devices.</description>
+				<default>false</default>
+			</parameter>
+			<parameter name="echo" type="boolean">
+				<label>RS485 Echo Mode</label>
+				<description><![CDATA[Flag for setting the RS485 echo mode
+				<br/>
+				<br/>This controls whether we should try to read back whatever we send on the line, before reading the response.
+				]]></description>
+				<default>false</default>
+				<advanced>true</advanced>
+			</parameter>
+			<parameter name="receiveTimeoutMillis" type="integer" min="0" unit="ms">
+				<label>Read Operation Timeout</label>
+				<description>Timeout for read operations. In milliseconds.</description>
+				<default>1500</default>
+				<advanced>true</advanced>
+			</parameter>
+			<parameter name="flowControlIn" type="text" multiple="false">
+				<label>Flow Control In</label>
+				<description>Type of flow control for receiving</description>
+				<default>none</default>
+				<!-- values here match SerialPort.FLOWCONTROL_* constants -->
+				<options>
+					<option value="none">None</option>
+					<option value="xon/xoff in">XON/XOFF</option>
+					<option value="rts/cts in">RTS/CTS</option>
+				</options>
+			</parameter>
+			<parameter name="flowControlOut" type="text" multiple="false">
+				<label>Flow Control Out</label>
+				<description>Type of flow control for sending</description>
+				<default>none</default>
+				<!-- values here match SerialPort.FLOWCONTROL_* constants -->
+				<options>
+					<option value="none">None</option>
+					<option value="xon/xoff out">XON/XOFF</option>
+					<option value="rts/cts out">RTS/CTS</option>
+				</options>
+			</parameter>
+
+			<!-- connection handling -->
+			<parameter name="timeBetweenTransactionsMillis" type="integer" min="0" unit="ms">
+				<label>Time Between Transactions</label>
+				<description>How long to delay we must have at minimum between two consecutive MODBUS transactions. In milliseconds.</description>
+				<default>35</default>
+			</parameter>
+			<parameter name="connectMaxTries" type="integer" min="1">
+				<label>Maximum Connection Tries</label>
+				<description>How many times we try to establish the connection. Should be at least 1.</description>
+				<default>1</default>
+				<advanced>true</advanced>
+			</parameter>
+			<parameter name="connectTimeoutMillis" type="integer" min="0" unit="ms">
+				<label>Timeout for Establishing the Connection</label>
+				<description>The maximum time that is waited when establishing the connection. Value of zero means that system/OS
+					default is respected. In milliseconds.</description>
+				<default>10000</default>
+				<advanced>true</advanced>
+			</parameter>
+		</config-description>
+	</bridge-type>
+</thing:thing-descriptions>

bundles/org.openhab.binding.modbus/src/main/resources/OH-INF/thing/bridge-tcp.xml

@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<thing:thing-descriptions bindingId="modbus"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:thing="https://openhab.org/schemas/thing-description/v1.0.0"
+	xsi:schemaLocation="https://openhab.org/schemas/thing-description/v1.0.0 https://openhab.org/schemas/thing-description-1.0.0.xsd">
+	<bridge-type id="tcp">
+		<label>Modbus TCP Slave</label>
+		<description>Endpoint for Modbus TCP slaves</description>
+		<config-description>
+			<parameter name="host" type="text" required="true">
+				<label>IP Address or Hostname</label>
+				<description>Network address of the device</description>
+				<default>localhost</default>
+				<context>network-address</context>
+			</parameter>
+			<parameter name="port" type="integer">
+				<label>Port</label>
+				<description>Port of the slave</description>
+				<default>502</default>
+			</parameter>
+
+			<parameter name="id" type="integer">
+				<label>Id</label>
+				<description>Slave id. Also known as station address or unit identifier.</description>
+				<default>1</default>
+			</parameter>
+
+			<parameter name="enableDiscovery" type="boolean">
+				<label>Discovery Enabled</label>
+				<description>When enabled we try to find a device specific handler. Turn this on if you're using one of the
+					supported devices.</description>
+				<default>false</default>
+			</parameter>
+
+			<!-- connection handling -->
+			<parameter name="timeBetweenTransactionsMillis" type="integer" min="0" unit="ms">
+				<label>Time Between Transactions</label>
+				<description>How long to delay we must have at minimum between two consecutive MODBUS transactions. In milliseconds.
+				</description>
+				<default>60</default>
+			</parameter>
+			<parameter name="timeBetweenReconnectMillis" type="integer" min="0" unit="ms">
+				<label>Time Between Reconnections</label>
+				<description>How long to wait to before trying to establish a new connection after the previous one has been
+					disconnected. In milliseconds.</description>
+				<default>0</default>
+				<advanced>true</advanced>
+			</parameter>
+			<parameter name="connectMaxTries" type="integer" min="1">
+				<label>Maximum Connection Tries</label>
+				<description>How many times we try to establish the connection. Should be at least 1.</description>
+				<default>1</default>
+				<advanced>true</advanced>
+			</parameter>
+			<parameter name="reconnectAfterMillis" type="integer" min="0" unit="ms">
+				<label>Reconnect Again After</label>
+				<description>The connection is kept open at least the time specified here. Value of zero means that connection is
+					disconnected after every MODBUS transaction. In milliseconds.</description>
+				<default>0</default>
+				<advanced>true</advanced>
+			</parameter>
+			<parameter name="connectTimeoutMillis" type="integer" min="0" unit="ms">
+				<label>Timeout for Establishing the Connection</label>
+				<description>The maximum time that is waited when establishing the connection. Value of zero means that system/OS
+					default is respected. In milliseconds.</description>
+				<default>10000</default>
+				<advanced>true</advanced>
+			</parameter>
+		</config-description>
+	</bridge-type>
+</thing:thing-descriptions>

bundles/org.openhab.binding.modbus/src/main/resources/OH-INF/thing/thing-data.xml

@@ -0,0 +1,146 @@
+<thing:thing-descriptions bindingId="modbus"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:thing="https://openhab.org/schemas/thing-description/v1.0.0"
+	xsi:schemaLocation="https://openhab.org/schemas/thing-description/v1.0.0 https://openhab.org/schemas/thing-description-1.0.0.xsd">
+	<thing-type id="data">
+		<supported-bridge-type-refs>
+			<bridge-type-ref id="poller"/>
+			<bridge-type-ref id="tcp"/>
+			<bridge-type-ref id="serial"/>
+		</supported-bridge-type-refs>
+		<label>Modbus Data</label>
+		<description>Data thing extracts values from binary data received from Modbus slave. Similarly, it it responsible of
+			tranlating openHAB commands to Modbus write requests</description>
+		<channels>
+			<channel id="number" typeId="number-type"/>
+			<channel id="switch" typeId="switch-type"/>
+			<channel id="contact" typeId="contact-type"/>
+			<channel id="dimmer" typeId="dimmer-type"/>
+			<channel id="datetime" typeId="datetime-type"/>
+			<channel id="string" typeId="string-type"/>
+			<channel id="rollershutter" typeId="rollershutter-type"/>
+			<channel id="lastReadSuccess" typeId="last-successful-read-type"/>
+			<channel id="lastReadError" typeId="last-erroring-read-type"/>
+			<channel id="lastWriteSuccess" typeId="last-successful-write-type"/>
+			<channel id="lastWriteError" typeId="last-erroring-write-type"/>
+		</channels>
+		<config-description>
+			<!-- what to read -->
+			<parameter name="readStart" type="text" pattern="^(0|[1-9][0-9]*(\.[0-9]{1,2})?)?$">
+				<label>Read Address</label>
+				<description><![CDATA[Start address to start reading the value. Use empty for write-only things.
+				<br />
+				<br />Input as zero-based index number, e.g. in place of 400001 (first holding register), use the address 0.  Must be between (poller start) and (poller start + poller length - 1) (inclusive).
+				<br />
+				<br />With registers and value type less than 16 bits, you must use X.Y format where Y specifies the sub-element to read from the 16 bit register:
+				<ul>
+					<li>For example, 3.1 would mean pick second bit from register index 3 with bit value type. </li>
+					<li>With int8 valuetype, it would pick the high byte of register index 3.</li>
+				</ul>
+				]]>
+				</description>
+			</parameter>
+			<parameter name="readTransform" type="text">
+				<label>Read Transform</label>
+				<description><![CDATA[Transformation to apply to polled data, after it has been converted to number using readValueType
+	<br /><br />Use "default" to communicate that no transformation is done and value should be passed as is.
+	<br />Use SERVICENAME(ARG) to use transformation service.
+	<br />Any other value than the above types will be interpreted as static text, in which case the actual content of the polled
+		value is ignored.]]></description>
+				<default>default</default>
+			</parameter>
+			<parameter name="readValueType" type="text">
+				<label>Read Value Type</label>
+				<description><![CDATA[How data is read from modbus. Use empty for write-only things.
+
+				<br /><br />With registers all value types are applicable.]]></description>
+				<options>
+					<option value="int64">64bit signed integer (int64)</option>
+					<option value="uint64">64bit unsigned integer (uint64)</option>
+					<option value="int64_swap">64bit signed integer, 16bit words in reverse order (dcba) (int64_swap)</option>
+					<option value="uint64_swap">64bit unsigned integer, 16bit words in reverse order (dcba) (uint64_swap)</option>
+
+					<option value="float32">32bit floating point (float32)</option>
+					<option value="float32_swap">32bit floating point, 16bit words swapped (float32_swap)</option>
+
+					<option value="int32">32bit signed integer (int32)</option>
+					<option value="uint32">32bit unsigned integer (uint32)</option>
+					<option value="int32_swap">32bit signed integer, 16bit words swapped (int32_swap)</option>
+					<option value="uint32_swap">32bit unsigned integer, 16bit words swapped (uint32_swap)</option>
+
+					<option value="int16">16bit signed integer (int16)</option>
+					<option value="uint16">16bit unsigned integer (uint16)</option>
+
+					<option value="int8">8bit signed integer (int8)</option>
+					<option value="uint8">8bit unsigned integer (uint8)</option>
+
+					<option value="bit">individual bit (bit)</option>
+				</options>
+			</parameter>
+			<parameter name="writeStart" type="text">
+				<label>Write Address</label>
+				<description><![CDATA[Start address of the first holding register or coil in the write. Use empty for read-only things.
+				<br />Use zero based address, e.g. in place of 400001 (first holding register), use the address 0. This address is passed to data frame as is.]]></description>
+			</parameter>
+			<parameter name="writeType" type="text">
+				<label>Write Type</label>
+				<description><![CDATA[Type of data to write. Leave empty for read-only things.
+				<br />
+				<br />
+				Coil uses function code (FC) FC05 or FC15. Holding register uses FC06 or FC16. See writeMultipleEvenWithSingleRegisterOrCoil parameter.]]></description>
+				<options>
+					<option value="coil">coil, or digital out (DO)</option>
+					<option value="holding">holding register</option>
+				</options>
+			</parameter>
+			<parameter name="writeTransform" type="text">
+				<label>Write Transform</label>
+				<description><![CDATA[Transformation to apply to received commands.
+	<br /><br />Use "default" to communicate that no transformation is done and value should be passed as is.
+	<br />Use SERVICENAME(ARG) to use transformation service.
+	<br />Any other value than the above types will be interpreted as static text, in which case the actual content of the command
+	value is ignored.]]></description>
+				<default>default</default>
+			</parameter>
+			<parameter name="writeValueType" type="text">
+				<label>Write Value Type</label>
+				<description><![CDATA[How data is written to modbus. Only applicable to registers, you can leave this undefined for coil.
+				<br /><br />Negative integers are encoded with two's complement, while positive integers are encoded as is.
+				]]>
+				</description>
+				<options>
+					<option value="int64">64bit positive or negative integer, 4 registers (int64, uint64)</option>
+					<option value="int64_swap">64bit positive or negative integer, 4 registers but with 16bit words/registers in reverse
+						order (dcba)
+						(int64_swap, uint64_swap)</option>
+					<option value="float32">32bit floating point (float32)</option>
+					<option value="float32_swap">32bit floating point, 16bit words swapped (float32_swap)</option>
+					<option value="int32">32bit positive or negative integer, 2 registers (int32, uint32)</option>
+					<option value="int32_swap">32bit positive or negative integer, 2 registers but with 16bit words/registers in reverse
+						order (ba)
+						(int32_swap, uint32_swap)</option>
+					<option value="int16">16bit positive or negative integer, 1 register (int16, uint16)</option>
+					<option value="bit">individual bit (bit)</option>
+				</options>
+			</parameter>
+			<parameter name="writeMultipleEvenWithSingleRegisterOrCoil" type="boolean">
+				<label>Write Multiple Even with Single Register or Coil</label>
+				<default>false</default>
+				<description><![CDATA[Whether single register / coil of data is written using FC16 ("Write Multiple Holding Registers") / FC15 ("Write Multiple Coils"), respectively.
+				<br />
+				<br />If false, FC6/FC5 are used with single register and single coil, respectively.]]></description>
+			</parameter>
+			<parameter name="writeMaxTries" type="integer" min="1">
+				<label>Maximum Tries When Writing</label>
+				<default>3</default>
+				<description>Number of tries when writing data, if some of the writes fail. For single try, enter 1.</description>
+			</parameter>
+			<parameter name="updateUnchangedValuesEveryMillis" type="integer" min="0" unit="ms">
+				<label>Interval for Updating Unchanged Values</label>
+				<default>1000</default>
+				<description>Interval to update unchanged values. Normally unchanged values are not updated. In milliseconds.</description>
+				<advanced>true</advanced>
+			</parameter>
+		</config-description>
+	</thing-type>
+</thing:thing-descriptions>

bundles/org.openhab.binding.modbus/src/main/resources/OH-INF/thing/thing-types.xml

@@ -0,0 +1,66 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<thing:thing-descriptions bindingId="modbus"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:thing="https://openhab.org/schemas/thing-description/v1.0.0"
+	xsi:schemaLocation="https://openhab.org/schemas/thing-description/v1.0.0 https://openhab.org/schemas/thing-description-1.0.0.xsd">
+	<channel-type id="switch-type">
+		<item-type>Switch</item-type>
+		<label>Value as Switch</label>
+		<description>Switch item channel</description>
+	</channel-type>
+	<channel-type id="contact-type">
+		<item-type>Contact</item-type>
+		<label>Value as Contact</label>
+		<description>Contact item channel</description>
+	</channel-type>
+	<channel-type id="datetime-type">
+		<item-type>DateTime</item-type>
+		<label>Value as DateTime</label>
+		<description>DateTime item channel</description>
+	</channel-type>
+	<channel-type id="dimmer-type">
+		<item-type>Dimmer</item-type>
+		<label>Value as Dimmer</label>
+		<description>Dimmer item channel</description>
+	</channel-type>
+	<channel-type id="rollershutter-type">
+		<item-type>Rollershutter</item-type>
+		<label>Value as Rollershutter</label>
+		<description>Rollershutter item channel</description>
+	</channel-type>
+	<channel-type id="string-type">
+		<item-type>String</item-type>
+		<label>Value as String</label>
+		<description>String item channel</description>
+	</channel-type>
+	<channel-type id="number-type">
+		<item-type>Number</item-type>
+		<label>Value as Number</label>
+		<description>Number item channel</description>
+		<config-description></config-description>
+	</channel-type>
+	<channel-type id="last-successful-read-type">
+		<item-type>DateTime</item-type>
+		<label>Last Successful Read</label>
+		<description>Date of last read</description>
+		<config-description></config-description>
+	</channel-type>
+	<channel-type id="last-erroring-read-type">
+		<item-type>DateTime</item-type>
+		<label>Last Erroring Read</label>
+		<description>Date of last read error</description>
+		<config-description></config-description>
+	</channel-type>
+	<channel-type id="last-successful-write-type">
+		<item-type>DateTime</item-type>
+		<label>Last Successful Write</label>
+		<description>Date of last write</description>
+		<config-description></config-description>
+	</channel-type>
+	<channel-type id="last-erroring-write-type">
+		<item-type>DateTime</item-type>
+		<label>Last Erroring Write</label>
+		<description>Date of last write error</description>
+		<config-description></config-description>
+	</channel-type>
+</thing:thing-descriptions>

bundles/org.openhab.binding.modbus/src/test/java/org/openhab/binding/modbus/internal/AtomicStampedKeyValueTest.java

@@ -0,0 +1,174 @@
+/**
+ * Copyright (c) 2010-2020 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.modbus.internal;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.assertThat;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.junit.MockitoJUnitRunner;
+
+/**
+ * @author Sami Salonen - Initial contribution
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class AtomicStampedKeyValueTest {
+
+    @Test(expected = NullPointerException.class)
+    public void testInitWithNullValue() {
+        new AtomicStampedValue<>(0, null);
+    }
+
+    @Test
+    public void testGetters() {
+        Object val = new Object();
+        AtomicStampedValue<Object> keyValue = new AtomicStampedValue<>(42L, val);
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(equalTo(val)));
+    }
+
+    @Test
+    public void testUpdateWithSameStamp() {
+        Object val = new Object();
+        AtomicStampedValue<Object> keyValue = new AtomicStampedValue<>(42L, val);
+        keyValue.update(42L, new Object());
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(not(equalTo(val))));
+    }
+
+    @Test
+    public void testUpdateWithDifferentStamp() {
+        Object val = new Object();
+        AtomicStampedValue<Object> keyValue = new AtomicStampedValue<>(42L, val);
+        keyValue.update(-99L, new Object());
+        assertThat(keyValue.getStamp(), is(equalTo(-99L)));
+        assertThat(keyValue.getValue(), is(not(equalTo(val))));
+    }
+
+    @Test
+    public void testCopy() {
+        Object val = new Object();
+        AtomicStampedValue<Object> keyValue = new AtomicStampedValue<>(42L, val);
+        AtomicStampedValue<Object> copy = keyValue.copy();
+
+        // unchanged
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(equalTo(val)));
+
+        // data matches
+        assertThat(keyValue.getStamp(), is(equalTo(copy.getStamp())));
+        assertThat(keyValue.getValue(), is(equalTo(copy.getValue())));
+
+        // after update they live life of their own
+        Object val2 = new Object();
+        copy.update(-99L, val2);
+
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(equalTo(val)));
+
+        assertThat(copy.getStamp(), is(equalTo(-99L)));
+        assertThat(copy.getValue(), is(equalTo(val2)));
+    }
+
+    /**
+     * instance(stamp=x).copyIfStampAfter(x)
+     */
+    @Test
+    public void testCopyIfStampAfterEqual() {
+        Object key = new Object();
+        Object val = new Object();
+        AtomicStampedValue<Object> keyValue = new AtomicStampedValue<>(42L, val);
+        AtomicStampedValue<Object> copy = keyValue.copyIfStampAfter(42L);
+
+        // keyValue unchanged
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(equalTo(val)));
+
+        // data matches
+        assertThat(keyValue.getStamp(), is(equalTo(copy.getStamp())));
+        assertThat(keyValue.getValue(), is(equalTo(copy.getValue())));
+
+        // after update they live life of their own
+        Object key2 = new Object();
+        Object val2 = new Object();
+        copy.update(-99L, val2);
+
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(equalTo(val)));
+
+        assertThat(copy.getStamp(), is(equalTo(-99L)));
+        assertThat(copy.getValue(), is(equalTo(val2)));
+    }
+
+    /**
+     * instance(stamp=x-1).copyIfStampAfter(x)
+     */
+    @Test
+    public void testCopyIfStampAfterTooOld() {
+        Object val = new Object();
+        AtomicStampedValue<Object> keyValue = new AtomicStampedValue<>(42L, val);
+        AtomicStampedValue<Object> copy = keyValue.copyIfStampAfter(43L);
+
+        // keyValue unchanged
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(equalTo(val)));
+
+        // copy is null
+        assertThat(copy, is(nullValue()));
+    }
+
+    /**
+     * instance(stamp=x).copyIfStampAfter(x-1)
+     */
+    @Test
+    public void testCopyIfStampAfterFresh() {
+        Object val = new Object();
+        AtomicStampedValue<Object> keyValue = new AtomicStampedValue<>(42L, val);
+        AtomicStampedValue<Object> copy = keyValue.copyIfStampAfter(41L);
+
+        // keyValue unchanged
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(equalTo(val)));
+
+        // data matches
+        assertThat(keyValue.getStamp(), is(equalTo(copy.getStamp())));
+        assertThat(keyValue.getValue(), is(equalTo(copy.getValue())));
+
+        // after update they live life of their own
+        Object key2 = new Object();
+        Object val2 = new Object();
+        copy.update(-99L, val2);
+
+        assertThat(keyValue.getStamp(), is(equalTo(42L)));
+        assertThat(keyValue.getValue(), is(equalTo(val)));
+
+        assertThat(copy.getStamp(), is(equalTo(-99L)));
+        assertThat(copy.getValue(), is(equalTo(val2)));
+    }
+
+    @Test
+    public void testCompare() {
+        // equal, smaller, larger
+        assertThat(AtomicStampedValue.compare(new AtomicStampedValue<>(42L, ""), new AtomicStampedValue<>(42L, "")),
+                is(equalTo(0)));
+        assertThat(AtomicStampedValue.compare(new AtomicStampedValue<>(41L, ""), new AtomicStampedValue<>(42L, "")),
+                is(equalTo(-1)));
+        assertThat(AtomicStampedValue.compare(new AtomicStampedValue<>(42L, ""), new AtomicStampedValue<>(41L, "")),
+                is(equalTo(1)));
+
+        // Nulls come first
+        assertThat(AtomicStampedValue.compare(null, new AtomicStampedValue<>(42L, "")), is(equalTo(-1)));
+        assertThat(AtomicStampedValue.compare(new AtomicStampedValue<>(42L, ""), null), is(equalTo(1)));
+    }
+}