Still working on: an enclosure-compatible open-source version of the 2nd gen Nest thermostat. It reuses the enclosure, encoder ring, display, and mounts of the Nest but replaces the "thinking" part with an open-source PCB that can interact with Home Assistant.
- The encoder ring which works like an LED mouse, but in reverse: Fully reverse-engineered and on its own demo PCB
- The faceplate PCB, which does the actual control of the thermostat wires, has been laid out, but the first version missed a really-obvious problem involving the behavior on power-on with certain of the GPIO pins from the ESP32, so I've got rev 3 on order from the PCB manufacturer.
Nest Thermostats of the 1st and 2nd generation will no longer be supported by Google starting October 25, 2025. You will still be able to access temperature, mode, schedules, and settings directly on the thermostat – and existing schedules should continue to work uninterrupted. However, these thermostats will no longer receive software or security updates, will not have any Nest app or Home app controls, and Google will end support for other connected features like Home/Away Assist. It has been pretty-badly supported in Home Assistant for over a year anyway, missing important connected features.