Rack32 KNX Shield

by Frank McAlinden


Rack32 KNX Shield

Provides direct control and monitoring of KNXopen in new window devices over the KNX bus. Requires a KNX Bus Coupling Unit (BCU) similar to thisopen in new window.

By using this shield and a KNX BCU you can program your Rack32 to communicate directly with the KNX bus. This allows direct control of actuators without the need for any infrastructure (i.e. TCP/IP network, MQTT broker, automation rules engine).

The original intent for this was to provide a failover system in the case of network or MQTT failure.


  • Pass through for Rack32 I2C and SPI breakouts
  • I/O breakout for second I2C bus
  • Optocoupler to provide galvanic separation between the Rack32 and KNX BCU
  • 5x2 pin header for direct fixing of Siemens KNX BCUopen in new window

Supported Firmware

There is a fork of the State Monitor firmware hereopen in new window which includes support for this shield.

This branch adds the option to set a KNX group address in config for each input. If the device enters failover mode it will publish KNX telegrams to the configured KNX group address directly on the KNX bus. This has been tested and works well.

Additional Resources

Where to Buy


How is the KNX BCU powered? Answer: It is powered directly from the KNX bus

Maker Info

Maker: Frank McAlinden

Link: Frank McAlinden

Compatible With