Reverse Engineering a Christmas Tree #HamSunday #ReverseEngineering @paultag

Paul Tagliamonte takes on the daunting task of reverse engineering the  codes used to control a Christmas tree:

I figured that there was a fun “capstone” to be done here – the blind reverse engineering and implementation of the protocol my cheep Amazon power switch uses to turn on and off my Christmas Tree.

Since operation of this device is unlicensed, I figured I’d start looking in the ISM band. The most common band used that I’ve seen is the band starting at 433.05MHz up to 434.79MHz. I fired up my trusty waterfall tuned to a center frequency of 433.92MHz (since it’s right in the middle of the band, and it let me see far enough up and down the band to spot the remote) and pressed a few buttons. Imagine my surprise when I realize the operational frequency of this device is 433.920MHz, exactly dead center. Weird, but lucky!

See how one goes from finding bursts of RF to ones and zeros used to control the lights in the thoroughly documented post here.