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KNX / MQTT bridge in Go

This application, crafted in Go, facilitates seamless integration between your KNX installation and MQTT. Perfect for smart home enthusiasts and IoT integrators, this bridge offers customizable and efficient connectivity.

Features

  • Customizable Integration: Connect your KNX system with MQTT effortlessly.
  • Automatic Type Conversion: Provide an XML export from ETS, and the app will handle type conversions automatically.
  • Flexible MQTT Topics: Publish KNX events to MQTT topics formatted as knx/x/y/z, where x/y/z represents the group address. You can also configure the knx/ prefix and use names for group address sections.

KNX XML Export

To get the most out of this application, provide an ETS XML export of your group addresses and their datapoint types. This enables automatic conversion between raw types and ensures precise data handling. Without this export, you’ll be limited to handling raw bytes only.

Configuration

For a detailed guide on setting up and customizing the KNX/MQTT bridge, refer to the example configuration file. This file is thoroughly documented and provides comprehensive instructions for tailoring the bridge to your specific needs.

Please note that the default configuration logs at the info level, which does not include detailed logs of successfully read KNX messages. During the integration phase, you may want to adjust the log level to debug to see incoming messages and gain better visibility into the bridge's operations.

Usage

You can build the application yourself, but using Docker is often more convenient. Here’s how you can get started with Docker:

Docker

Note that binding to the host's network is only necessary if you connect to KNX over multicast, i.e. tunnelMode: false.

docker run --rm -it --network host -v $(pwd)/config.yaml:/app/config.yaml -v $(pwd)/knx.xml:/app/knx.xml pakerfeldt/knx-mqtt:latest

Docker Compose

services:
  knx-mqtt:
    image: pakerfeldt/knx-mqtt:latest
    restart: unless-stopped
    network_mode: "host"
    volumes:
      - ./config.yaml:/app/config.yaml
      - ./knx.xml:/app/knx.xml

To MQTT

MQTT message format

The app supports several payload formats for MQTT messages:

Type Description Requires KNX XML
value String representation of the value (e.g., 24.52) Yes
value-with-unit String representation including the unit (e.g., 24.42 °C) Yes
json JSON representation of the message Yes
bytes Raw bytes as specified by KNX No

When sending JSON messages, you can choose to include/exclude the following fields:

Field Description
bytes Raw bytes encoded in Base64
name Name of the group address
value String representation of the value
unit Associated unit of the value

To KNX

KNX group addresses can be referred to using either their group address knx/x/y/z/ or their full name, where x and y are the names of the group ranges and z is the name of the actual group address.

Sending read requests

To send a read request, write to knx/x/y/z/read with any payload.

Writing raw bytes to an address

To write to a group address with its raw bytes, send a message to knx/x/y/z/write-bytes with the bytes as payload.

Writing value as a string to an address

To write to a group address using a string representation, send a message to knx/x/y/z/write with the value as a string. E.g. "25.35", "true".

Supported KNX DPTs

See supported-dpts. Let me know if you're missing a specific DPT.

Migrating from knx-mqtt-bridge

If you’re transitioning from knx-mqtt-bridge, the NodeJS version of this bridge, you’ll find the migration relatively straightforward. The configurations are similar enough to make the transition smooth. This library might initially support fewer DPTs and TLS is not yet supported for MQTT.

Caveats

This app does not yet support MQTT over TLS.