“I had at last some time to work on the project. The prototype PCB is (at least, electrically) functional. I started with making the TMP102 temperature sensor work. Nothing to say in particular, it’s just an other I2C-small-package-sensor. Or rather SMBus, but apart from the minimum speed clock requirements on the SMBus, the two protocols are alike. On boot-up, the sensor gets configured and put to shutdown mode. Then, I use the “One Shot conversion” feature. When the right command is sent, the sensor starts a one-time temperature acquisition and returns to shutdown state, allowing to save as much as energy as possible. The precision of the sensor is typically 0.5°C over its standard temperature range (-25°C to +85°C, the one I’ll be using) and the resolution is 0,0625°C (the LSB). The temperature results are read on two bytes (12bits resolution). The first byte is the number before the comma, 2’s complemented for negative temperatures. The second byte contains the number after the comma. It has to be multiplied by 0.0625°C to get the real number.”