knx2mqtt - A KNX2MQTT Bridge allowing bidirectional telegram transfer

I've created this project as a replacement for the KNX integration of HomeAssistant that worked not stable in my environment.

It is quite simple and does what it's name says: It works as a bridge between KNX and MQTT tranlating messages between these in both directions.

Installation

The installation requires at least Python 3.9. On Raspbian, it is required to install rustc because xknx depends on cryptography which cannot be built without rust.

See Install Rust for details.

Philosophy is to install it under /usr/local/lib/knx2mqtt and control it via systemd.

cd /usr/local/lib
git clone https://github.com/gbeine/knx2mqtt.git
cd knx2mqtt
./install

The install script creates a virtual python environment using the venv module. All required libraries are installed automatically. Depending on your system this may take some time.

Configuration

The configuration is located in /etc/knx2mqtt.conf.

Each configuration option is also available as command line argument.

• copy knx2mqtt.conf.example
• configure as you like

option	default	arguments	comment
mqtt_host	'localhost'	-m, --mqtt_host	The hostname of the MQTT server.
mqtt_port	1883	--mqtt_port	The port of the MQTT server.
mqtt_keepalive	30	--mqtt_keepalive	The keep alive interval for the MQTT server connection in seconds.
mqtt_clientid	'fronius2mqtt'	--mqtt_clientid	The clientid to send to the MQTT server.
mqtt_user	-	-u, --mqtt_user	The username for the MQTT server connection.
mqtt_password	-	-p, --mqtt_password	The password for the MQTT server connection.
mqtt_topic	'fronius'	-t, --mqtt_topic	The topic to publish MQTT message.
knx_host	'localhost'	--knx_host	The address of the KNX tunnel device.
knx_port	3671	--knx_port	The port of the KNX tunnel device.
knx_local_ip	-	--knx_local_ip	The ip address of the system that connects to KNX.
knx_individual_address	-	--knx_individual_address	The group address of the system that send telegrams to KNX.
knx_no_queue	-	--knx_no_queue	Workaround for scheduling problems of XKNX telegram queue.
verbose	-	-v, --verbose	Be verbose while running.
-	'/etc/knx2mqtt.conf'	-c, --config	The path to the config file.
items	see below	-	The configuration for the items on the KNX bus.

KNX

Currently, only KNX tunneling mode is supported. It may become more in the future, if I found testing environments with according setups. Feel free to add routing or other options and open a pull request for this.

Items

Then you can configure your bus topology as items.

    ...
    "items": [
        {
            "address": "5/0/10",
            "type": "DPTTemperature"
        },
        {
            "address": "5/0/20",
            "type": "DPTHumidity"
        },
        ...
    ]
    ...

Each item need an address (the group address) and a type. Unfortunately, the list of types is not part of the xknx documentation. But the examples in the file I provide with the project may fit for the most purposes. All supported types can be found in the xknx sources.

The default operating mode for an object is to listen on the KNX and publish the telegram values to MQTT.

That may be changed using the following settings:

• mqtt_subscribe (default: false): if set to true, changes on any related MQTT topic will be processed

Publishing

All values are published using the group address and the MQTT topic.

So, the Date exposing sensor in the example is listening for home/bus/knx/0/0/1 and the switch is listening on and publishing to home/bus/knx/0/1/1.

Running knx2mqtt

I use systemd to manage my local services.

Support

I have not the time (yet) to provide professional support for this project. But feel free to submit issues and PRs, I'll check for it and honor your contributions.

License

The whole project is licensed under MIT license. Stay fair.