It has been a long time since I have worked with electronics. It seems like I haven’t really worked on anything in the last 6 years or so. The other day at our company meeting we all got these PixMob bracelets that were remotely controlled to glow different colors. During the meeting I realized I needed to reverse engineer them and figure out how they worked. First couple things that I noted was that there was that the unit was sonically welded together so it might be a little annoying to crack one open. There was a a black box in one corner that looked like an IR receiver. After looking around the place and playing a little bit I confirmed that it was running off of IR and that there were a bunch of transmitters in the ceiling. On the way out I was able to get my hands on a couple extras. Sadly, it wasn’t until after we left that I realized that I had been playing with blocking the IR right at the end, so while a bunch of other people had theirs “unlocked” so it would respond to movement, mine were stuck in presentation mode.
So I cracked one open today to see what was inside. Luckily there wasn’t any custom silicon. There was definitely a nice IR receiver and an ATtiny44A microcontroller. Yes! I had done a lot of work with the Atmel line in the pass, so this should be good.
After mapping out the board a little I pulled off the IR receiver. No markings so I won’t be able to just look up what frequency they are expecting, but hopefully I should be able to just test the receiver in isolation to figure out what it responds to.
Lucky for me they left everything in place to communicate with the microcontroller. On the edge of the board they left a bunch of pads for the serial programming port. I quickly soldered up some cables and hooked it up to one of my programmers.
I then realized that I never really finished my programmer software. I had built my own custom one because way back in the day it was really easy to build one off of a parallel port, so over the years I just always built my own. I was able to communicate with the Atmel, pull the fuse and lock bits. It looks like they might have locked the part, so I might not be able to read the flash out, but I’ll need to poke around a little more.