Some type of logger or sniffer exists for almost every form of electronic communication. Your keystrokes, phone conversations, and wireless networks could all be monitored. In this awesome proof-of-concept project, [James] expanded that array to include garage door openers. After receiving a piece of chain mail which stated that criminals have the technology to record any remote code and play it back, [James] wondered if he could build such a device that would work on at least his opener model.
[James] started off with a trip to the hardware store. He was unable to find both a transceiver that worked on the frequency of his remote control (308MHz clocked MAX7042 chip), so at least for this incarnation (he plans to build another one that is capable of replaying a captured signal), only a receiver was implemented. The receiver was connected to a logic analyzer in order to determine its protocol. Since the signal coming from the receiver was very low, [James] had to amplify it through a buffer before it could be detected.
An ATtiny26 and a 4 line x 20 character backlit LCD were used to interpret and display info from the receiver. [James] built the sniffer around a custom PCB (though he ran into a few layout errors that he had to fix post-production). All of the firmware was written in C. It is fairly straightforward, but takes up 98% of the microcontroller’s memory. The program is designed to monitor pin change interrupts and timers to filter out invalid codes as well as noise. Any info (the door codes that have been sniffed) is displayed through a 4-bit interface on the LCD, for easy recording. With the codes, one can configure another garage remote to open the door. If you have any suggestions for V2, We’re sure [James] will be reading the comments.
Update: The code and PCB files (with the error) are available through one of the following mirrors: