Not content with fitting a tiny square-wave MIDI synthesizer into a MIDI plug, [Mitxela] went on to cram a similar noisemaker into a USB plug itself.
Besides being physically small, the code is small too, as well as the budget. It uses V-USB for the USB library running on an ATtiny85, and a couple of passive parts. His firmware (apparently) takes in MIDI notes and spits out square waves.
Nothing too amazing, until you think about the miniaturization effort. To get this thing to fit inside the metal case of a USB plug, [Mitxela] cut out some of the plastic, and crammed the parts inside. And by “crammed” we mean ground everything down that wouldn’t fit. The through-hole Zener diodes were just a little bit too tall, so they went under the grinder. The end of the ATtiny stuck out just a tad. More grinding.
Once everything fit, it went back into the metal case with a bit of insulating tape, and it was done. Due to the form-factor alone, it was a lot smaller than his previous effort, and certainly even less useful! We see further room for miniaturization through trimming down the piezo buzzer case. We also see no point in that either.
This project seems to have started out as a finger-study for building USB MIDI controllers, so we’re looking forward to cool things coming down the pike. Until then, enjoy the so-far smallest monophonic USB MIDI squarewave synth that we’ve seen.