A revamped synth engine for a toy keyboard, with instrument presets and Midi out.

A friend gifted me a cheap toy musical keyboard. The sound quality was atrocious, and it could only play one note at a time. So I removed its circuitry while keeping its enclosure, speaker, and keybed, and with some tinkering and a Raspberry Pi Pico I turned it into something usable.

I made a video showing the makeover. The soundtrack is entirely played on the Picophonica, recorded one instrument at a time.

I integrated a software synthesizer into the Pico. It’s pico_synth_ex by Ryo Ishigaki – ISGK Instruments. The new engine boasts two oscillators, featuring descending sawtooth and square waveforms, a customizable filter with resonance control, cutoff modulation, a Decay-Sustain amp envelope, and an LFO for added modulation possibilities.
I managed to rewire a secondary keypad with fourteen keys, using it to recall the presets and change instrument parameters.
The existing, rather pointless 3.5mm microphone input found a new purpose as an audio output, while a USB-C port exposed through a simple adapter enables Midi-out functionality.

Source code

You can find the source code of the project here: github.com/TuriSc/Picophonica

Picophonica is an original project.

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