Embedded Lab

This Instructable describes how to build a wifi controlled thermostat that can be programmed over the internet as well as locally through a touchscreen TFT LCD display.

The system uses a Raspberry Pi as a central hub that serves web pages so I can control the thermostats from anywhere. The hub also handles all of the wireless communication over nRF24L01+ radio modules (I know I said “WiFi,” and the nRF24L01+ radio module isn’t technically WiFi, but more on that later), and maintains a MySQL database with the thermostat programming as well as any data logging I do. And finally, the hub runs two servers written in Python – one controls the thermostat (as an intermediary between the web-page and the thermostat) and the other handles data logging. I believe this could probably be done with the thermostats each serving its own simple web-page and sending data directly to the MySQL database. This would eliminate the need for the lighttpd web-server and the two python servers. But, I feel like doing this on the hub does provide the simplicity of a single web-site, and the python servers provide a lot of flexibility. Plus I don’t have to update the code on the thermostats whenever I want to make changes to these aspects.