Comfospot 50

Findings from reverse engineering the Zehnder Comfospot 50 to get it into Home Assistant.

Idea

While some efforts where made to analyze the serial connection on the main board of the ventilation system, I tried a more 'analog', less invasive route. The idea was to put a microcontroller behind the button controls on the front of the device and intercept and manipulate the signals coming from, and going to the control panel. To do this I had to find the correct connector. The Würth Electronics WR-MM IDC Connector System is used, with 14 Pins.

Pin Definitions

TO DO: Insert Pin definition picture

First I analyzed which pin was responsible for which button press and LED on the control panel. And the most important question was if there is a supply voltage to drive a microcontroller, preferably 3.3V.

PCB

I built a PCB which can be clipped directly onto the control panel and sit between it and the ecu of the system. On the PCB we need an WeAct ESP32 C3, a female and a male WR-MM connector.

Home Assistant Integration

For the programming of the microcontroller I settled on ESPHome, since I'm quite familiar with the system and I can integrate it without any additional work into Home Assistant.

All functions which can be controlled from the control panel can be controlled from within HA.

• fan speed (readout and control)
• fan direction / exchange
• change filter and error LED
• reset filter

While all of these functions can be controlled from within HA, the control panel remains fully functional, and every state change triggered on the device itself will be reflected in HA.

Limitations:

Comfospot can not be turned on remotely

Unfortunately the standby mode also cuts the power to the microcontroller and reenabling the fans remotely would not be possible anymore. A physical button press is required. To prevent this from happening accidentally a 'Turn Off locked' switch is active by default.

TO DO:

• Add Gerber files
• Add BOM
• Add YAML