While attempting to understand the mess of wires that is the Apollo-era space program Up-Data Link Confidence Test Set, Ken Shirriff decided to automate the manual probing process with an automatic connection tracing system that he calls the Beep-o-matic.

Ken Shirriff’s blog is a veritable smorgasbord of fascinating in-depth retrocomputing content, and he also documents his work extensively on Twitter. His reverse engineering of the Apollo Guidance Computer is a particularly fascinating project, and it is here that our humble Teensy 4.1 comes into play!

By combining three 16-bit PCA9555A GPIO chips with the appropriate connectors and a Teensy 4.1 over I2C, Ken can scan through all 47 pins in under a second, rather than laboriously listening for a multimeter beep while probing each manually.

A couple of Python scripts capture and process the output, and voila, you have … an extremely specific tool that is unlikely to be of use to anyone else on the planet? However! The same concept could certainly be applied to other reverse engineering problems, so take a look at the project details and code on GitHub, and let us know if you end up adapting the idea for other uses!