KNX Binding

Documentation of the KNX Binding Bundle

Introduction

The openHAB KNX binding allows to connect to KNX Home Automation installations. Switching lights on and off, activating your roller shutters or changing room temperatures are only some examples.

To access your KNX bus you either need an KNX IP gateway (like e.g. the Gira KNX IP Router) or a PC running EIBD (free open source component that enables communication with the KNX bus).

For installation of the binding, please see Wiki page Bindings.

Binding Configuration in openhab.cfg

You can find the configuration section for the KNX binding in file configurations/openhab.cfg, section "KNX Binding".

For your convenience you can see the relevant section as follows:

# KNX gateway IP address 
# (optional, if serialPort or connection type 'ROUTER' is specified)
knx:ip=

# KNX IP connection type. Could be either TUNNEL or ROUTER (optional, defaults to TUNNEL)
# Note: If you cannot get the ROUTER mode working (even if it claims it is connected), 
# use TUNNEL mode instead with setting both the ip of the KNX gateway and the localIp.
knx:type=

# KNX gateway port (optional, defaults to 3671)
knx:port=

# Local endpoint to specify the multicast interface, no port is used (optional)
knx:localIp=

# Serial port of FT1.2 KNX interface (ignored, if ip is specified)
# Valid values are e.g. COM1 for Windows and /dev/ttyS0 or /dev/ttyUSB0 for Linux
knx:serialPort=

# Pause in milliseconds between two read requests on the KNX bus during
# initialization (optional, defaults to 50)
knx:pause=

# Timeout in milliseconds to wait for a response from the KNX bus (optional, 
# defaults to 10000)
knx:timeout=

# Number of read retries while initialization items from the KNX bus (optional,
# defaults to 3)
knx:readRetries=

# Seconds between connect retries when KNX link has been lost
# 0 means never retry, it will only reconnect on next write or read request
# Note: without periodic retries all events will be lost up to the next read/write request
# (optional, default is 0)
knx:autoReconnectPeriod=

A sample configuration could look like:

knx:ip=192.168.1.10
knx:type=ROUTER

Bind Items to KNX

Description

In order to bind an item to a KNX device you need to provide configuration settings. The easiest way to do so is to add binding information in your 'item file' (in the folder configurations/items`). The syntax for the KNX binding configuration string is explained here:

knx="[<][<dptId>:]<mainGA>[[+[<]<listeningGA>]+[<]<listeningGA>..], [<][<dptId>:]<mainGA>[[+[<]<listeningGA>]+[<]<listeningGA>..]"

where parts in brackets [] signify an optional information.

Each comma-separated section corresponds to a KNX datapoint. There is usually one datapoint defined per accepted command type of an openHAB item. If no datapoint type id is defined for the datapoint, this is automatically derived from the list of accepted command types of the item - i.e. the second datapoint definition is mapped to the second accepted command type of the item.

The optional '<' sign tells whether the group address of the datapoint accepts read requests on the KNX bus (it does, if the sign is there).

Each itemtype (see page Items) accepts different command types. When binding an item to KNX you can provide one KNX group address ("mainGA") and several listening group addresses ("listeningGA") to each commandtype.

mainGAs are used for updating the status of an openHAB items via KNX. There can only be one mainGA for an openHAB item (Highlander principle :-) listeningGAs are used for obtaining status changes from KNX. There can be multiple listeningGAs for one item.

Example

Given we want to bind a Dimmer Item to KNX, we have first to check which commands an openHAB dimmer item does accept:

On page Items we that an openHAB Dimmer Item accepts three types of commands:

Itemname	Description	Command Types
Dimmer	Item carrying a percentage value for dimmers	OnOff, IncreaseDecrease, Percent

Also in the sources, we can find this information:

acceptedCommandTypes.add(OnOffType.class);
acceptedCommandTypes.add(IncreaseDecreaseType.class);
acceptedCommandTypes.add(PercentType.class);

So, we first have to bind the OnOff command to the respective KNX group addresses, then the IncreaseDecrease command and finally the Percentage command. Please note that the sequence of these commands is relevant.

In our example we assign the following KNX group addresses to the different commands:

Command Type	Main Group Address	Listening Address(es)	Comment
OnOff command	1/3/20	0/3/20	-
IncreaseDecreaseCommand	1/3/21	-	no listening GAs here as INCREASE and DECREASE are only commands but not valid states
PercentCommand	1/3/22	0/3/22 and 0/8/15

The respective line in the items definition file would therefore look like this:

Dimmer TestDimmer (Lights) { knx="1/3/20+0/3/20, 1/3/21, 1/3/22+0/3/22+0/8/15" }

If you have a dimmer that does not support INCREASE/DECREASE commands and you thus do not have a GA to provide in the middle, you can also directly define the datapoint types (DPTs) in the configuration. The above example would then look like this (without INCREASE/DECREASE support):

Dimmer TestDimmer (Lights) { knx="1.001:1/3/20+0/3/20, 5.004:1/3/22+0/3/22+0/8/15" }

Command types for items

For identifying the different command types for items, please either have a look into the openHAB source code or see Wiki page Items.

Further examples

Here are some further examples for valid binding configuration strings:

For a SwitchItem:

knx="1/1/10"
knx="1.001:1/1/10"
knx="<1/1/10"
knx="<1/1/10+0/1/13+0/1/14+0/1/15"
knx="1/1/10+<0/1/13+0/1/14+0/1/15"

For a RollershutterItem:

knx="4/2/10"
knx="4/2/10, 4/2/11"
knx="4/2/10, 4/2/11, 4/2/12"
knx="1.008:4/2/10, 5.006:4/2/11"
knx="<4/2/10+0/2/10, 5.006:4/2/11+0/2/11"

As a result, your lines in the items file might look like the following:

/* Lights */
Switch Light_GF_Living_Table "Table" (GF_Living, Lights) { knx="1/1/10+0/1/5" }

/* Rollershutters Up/Down, Stop/Move */
Rollershutter Shutter_GF_Living "Shutter" (GF_Living, Shutters) { knx="4/2/10, 4/2/11" }

/* Rollershutters  Up/Down, Stop/Move, Position */
Rollershutter Shutter_GF_Living "Shutter" (GF_Living, Shutters) { knx="4/2/10, 4/2/11, 4/2/12" }

/* Indoor Temperatures */
Number Temperature_GF_Living "Temperature [%.1f °C]" <temperature> (GF_Living) { knx="<5/2/12" }

Further KNX binding examples can be found in our openhab-samples WIKI: KNX Binding Examples

Supported Datapoint Types

The KNX binding supports a limited set of Datapoint types (DPTs). If your item configuration contains a DPT that is not supported by the KNX binding, openHAB 1.4.0 and later will throw an exception during startup ("DPT n.nnn is not supported by the KNX binding").

To get an overview of the supported DPTs, it's best to look into the source code of the KNX binding and the library it depends on. The DPTs for the binding are defined in KNXCoreTypeMapper. The constants (and their mapping to DPTs) are defined in the library calimero.