The Duco Connectivity Board was reverse-engineered and found to actually be an ESP32 in disguise, offering limited control options for the ventilation system. Using hardware reverse engineering and protocol analysis, it was discovered that the system did not operate on Modbus, leading to the decoding of unique protocol messages. By adjusting mode settings and comfort temperature through the web interface, communication patterns were identified. Further analysis revealed how to read the comfort temperature, the current mode, and CO2 sensor readings. This information enabled the creation of an ESPhome component for more advanced control. The detailed process and findings are documented in the GitHub PR: esphome/esphome#7993.
https://github.com/kokx/duco-analysis