- User Arduino IDE to program the NodeMCU
- Use MQTT to communicate boiler, remote and controller unit (https://en.wikipedia.org/wiki/MQTT)
- Boiler and remote units to be a NodeMCU (https://nodemcu.readthedocs.io/en/master/)
- Remote Units to include an output pin controlled by a MQTT subscription. This can be used to drive the relay, a signaling LED or leave disconnected.
- Controller unit to be an always on Raspberry Pi. It receives room temperatures from remote units and commands boiler ON/OFF accordingly.
- Remote units to make use of low power modes, disconnect WiFi between updates... not really to use batteries. Consider getting power from 24V thermostat circuit. (https://www.sparkfun.com/news/1842)
Is different the configuration for HomeAssistant instead OpenHab?