An MP3 Player That Only Works Inside a Tape Deck
Jonathan Rowny built a digital music player in a cassette shell: an ESP32-S3 with a microSD reader and a PCM5102 I2S codec, outputting audio through the deck's read head. SLA-printed gears transfer motion between the spools so the deck's auto-stop and auto-reverse never trigger. He notes he didn't account for capstan motion — a fix for the next revision.