What was done
An ESPHome and Home Assistant integration passively decodes telemetry from a Harvia Griffin WX350 display on a CG170 heater control unit.
This hobbyist project reverse engineers the RS-485 connection between a Harvia Griffin WX350 wall display and a CG170 sauna heater control unit. The repository describes the work as AI-assisted and provides an ESPHome integration with a dual-channel passive sniffer and real-time telemetry bridge.
Current capabilities
The project reports that it has been tested with an original WX350 display connected to a conventional CG170 electric heater. It decodes the remaining sauna timer and tracks heater, light and fan relay status. The ESPHome setup connects through the low-voltage display cable and reports the data to Home Assistant. The repository also documents bus protocol details and its hardware setup.
Current limits and safety
A full inline man-in-the-middle controller and filtering of spurious E9 errors are stated as future goals, not current capabilities. The README says the integration has not been tested with Griffin Combi, Griffin Infrared, Harvia Xenio or other heater models. It limits physical connections to the 12V DC/3.3V logic cable and warns users not to open or touch the heater’s mains compartment.
The author does not identify the AI model or specify which reverse-engineering steps it performed. The reported AI assistance and documented protocol work meet the directory’s inclusion threshold, but the model and work split remain unreported.