Over on YouTube Adam Łoboda has uploaded a video showing the full steps that he's taken to reverse engineer and clone a wireless garage door key using an RTL-SDR and Arduino.
He starts by using the Universal Radio Hacker software to record a copy of the wireless signal generated by the garage key. Using the software he can then analyze the signal, and determine the preamble data, payload data and pulse width which he can then input into some Arduino code. The Arduino can then generate an identical signal, and transmit it via a cheap FS1000A 433 MHz RF module. Finally, at the end of the video Adam shows the cloned Arduino based garage key working as expected.
hacking & clonning my garage key with URH ( Universal radio Hacker ) and ARDUINO DIGISPARK + FS1000A
Johannes Smit wanted to be able to view the live data from his SWR WH2303 weather station and send it to a database. Whilst the weather data acquisition software that he paid for worked well, he thought that there must be a cheaper and more fun way to grab the data. But unfortunately the manufacturers would not respond to his request for the RF protocol specifications. So Johannes decided to reverse engineer the protocol using his RTL-SDR instead.
Next he fired up Universal Radio Hacker (URH) and captured a sample of the weather station signal. Using URH he was able to determine the modulation type (FSK) and the bit length parameter (150us). Johannes' next step was to open the weather station, find the RF chip, look up the RF chip information on the web and find the spec sheet. From the spec sheet and internet forum searches he was able to determine the properties of the packet including the sync word and preamble. With this data he was able to determine the packet structure.
Finally he captured a packet and recorded the exact data shown on the weather station at the time of the packet. With this he was able to search the binary data string for the data shown on the weather station, indicating the location of a particular piece of data within the string.
Johannes' tutorial shows just how powerful tools like Universal Radio Hacker can be, and his tutorial is an excellent start for those looking at reverse engineering any of their own local RF protocols.