Simple MIDI synth squeezed into a USB plug
A few months after creating what was claimed to be the world's smallest MIDI synthesizer, which was smaller than the capsule at the end of a 5-pin DIN cable, a self-confessed MIDI lover and prolific electronics tinkerer has managed to cram a tone generating circuit into the black plastic frame inside a USB plug.
The project began by taking a metal-encased USB plug apart to reveal the plastic frame. This was then trimmed and scraped out to make room for the circuit components. The pins were cut back and the electronics installed, which included Zener diodes flattened with a grinding wheel, capacitors and an ATtiny85 microcontroller. The circuit was covered with kapton insulation tape to help prevent it from shorting and the metal housing replaced before attaching a piezo buzzer to output the monophonic "chiptunes."
Its creator, Tim Jacobs, reckons that the build took no more than 5 hours and admits that the device is completely pointless. There are none of the envelopes, filters or oscillators you might associate with a genuine synthesizer. It's only able to function when plugged into a computer or laptop, generating square waves from MIDI data.
But he says that it wasn't built to be useful, rather for the challenge of putting it together. And in that respect, it succeeds magnificently. A walkthrough of the creation process and an example of the chirpy tunes it throws out can be seen in the video below.