Cheap weather stations send their outdoor readings over 433 MHz radio. Pogodynka (“weather station” in Polish) listens to an Auriol sensor with an RFM83C receiver and an Arduino, and decodes the packets itself.
The protocol codes bits by the gap between pulses. A long sync gap comes first. After it, a gap of about 4.5 ms is a one and about 2.5 ms is a zero. An interrupt records the timing of every pulse into a ring buffer. A small state machine finds the sync, collects the bits into nibbles and builds a packet.
The repository keeps the documents it is based on: the receiver datasheet and a community description of the Auriol protocol.