Inventive designer Salvatore “Turi” Scandurra has given a youngsters’s toy keyboard a serious overhaul to create the Picophonica, a fully-functional synth powered by a Raspberry Pi Pico and its dual-core RP2040 microcontroller.

“A buddy gifted me an inexpensive toy musical keyboard,” Scandurra explains of the origins of the Picophonica undertaking. “The sound high quality was atrocious, and it might solely play one observe at a time. So I eliminated its circuitry whereas protecting its enclosure, speaker, and keybed, and with some tinkering and a Raspberry Pi Pico I turned it into one thing usable.”

Mother and father, in addition to these with a private curiosity in low-cost plastic tat, can be aware of the fashion of keyboard picked for the undertaking. Whereas technically practical, they’re very a lot a single voice affair — taking part in again a pitch-shifted pattern relying on key pressed, and sometimes set at a non-adjustable quantity seemingly fastidiously chosen to drive any adults within the neighborhood to despair.

The Picophonica just isn’t one in every of these — not less than, any extra. As an alternative, the housing performs host to a Raspberry Pi Pico growth board and its dual-core Arm Cortex-M0+ RP2040 microcontroller working a Scandurra’s adaptation of a synth engine initially written by ISGK Devices’ Ryo Ishigaki.

“The brand new engine boasts two oscillators, that includes descending sawtooth and sq. waveforms, a customizable filter with resonance management, cut-off modulation, a decay-sustain amp envelope, and an LFO [Low-Frequency Oscillator] for added modulation potentialities,” Scandurra explains. “In my construct I managed to rewire a secondary keypad with fourteen keys, utilizing it to recall the presets and alter instrument parameters.”

The matrix of the unique keyboard is wired to the Raspberry Pi by way of its general-purpose enter/output (GPIO) pins, with one other used to supply analog audio output by way of pulse-width modulation (PWM). “The present, somewhat pointless, 3.5mm microphone enter discovered a brand new goal as an audio output,” Scandurra provides, an enlargement which works alongside the on-board amplified speaker, “whereas a USB [Type]-C port uncovered by means of a easy adapter permits MIDI-out performance.”

Extra info on Scandurra’s construct is out there on his weblog, whereas supply code and a schematic for an amplifier ought to one be required could be discovered on GitHub below the permissive MIT license.