@th One of my favorite reverse-engineering stories is the person who "blinked" the contents of the firmware of a Canon camera out through an LED, and used a photodiode (from a ball mouse) connected to their microphone jack to record the binary as an audio file.
https://chdk.fandom.com/wiki/Obtaining_a_firmware_dump#Hardware-software_solution
@th i got so frustrated that i programmed Morse into an led.