My Thermostat Was Speaking an Industrial Protocol. Just Not to Me.

A senior software engineer with limited hardware experience successfully reverse-engineered a proprietary BACnet MS/TP thermostat to integrate it into their home automation system. Faced with a lack of documentation and the risk of disrupting a shared industrial HVAC bus, the author utilized an ESP32-S3 gateway to communicate with the device. By carefully studying the RS-485 bus traffic and implementing a non-blocking firmware architecture, the engineer mapped over 50 objects, allowing for remote control of heating and cooling zones. The project highlights the intersection of software engineering discipline and hardware hacking, emphasizing the importance of safety protocols when interfacing with live industrial systems. The author credits AI tools for assisting with hardware selection and protocol research, while noting that the critical reverse-engineering work required manual, hands-on verification to ensure system stability and avoid bus collisions.