As I like to have plants at home but always forgot to water them, I bought a cheap resistive soil moisture sensor. Actually, it is just two strips of copper wired as a voltage divider with a 10k resistor, the IC is used as a comparator to have a “digital” output, with a threshold set by the trimpot.

As a part of my future home automation called NoteRF, I need some devices other than a Raspberry Pi grabbing weather and pollution data from the internet: I designed a PCB and throw some lines of code on it.
Currently, the devices are only sensors, but I plan to implement some actuators later. Everything communicates wirelessly with the help of HopeRF RFM69hw, I will write something on the PCB and publish them as soon as I have the time to do some minor corrections to the Eagle files.

I wanted to use sleep functions of the Atmega328 (in power-down mode), in conjunction with Arduino’s software serial library: it turns out that all interrupt vectors are enabled in sleep mode.