Artistic designer Salvatore “Turi” Scandurra has given a kids’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 good friend gifted me an inexpensive toy musical keyboard,” Scandurra explains of the origins of the Picophonica mission. “The sound high quality was atrocious, and it might solely play one word at a time. So I eliminated its circuitry whereas retaining 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, might be acquainted with the model of keyboard picked for the mission. Whereas technically useful, they’re very a lot a single voice affair — taking part in again a pitch-shifted pattern relying on key pressed, and usually set at a non-adjustable quantity seemingly rigorously chosen to drive any adults within the neighborhood to despair.
The Picophonica just isn’t one among these — no less than, any extra. As a substitute, 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.”
Many of the keyboard’s guts have been eliminated, changed by a Raspberry Pi Pico growth board. (📷: Turi Scandurra)
The matrix of the unique keyboard is wired to the Raspberry Pi through its general-purpose enter/output (GPIO) pins, with one other used to offer analog audio output through pulse-width modulation (PWM). “The prevailing, relatively pointless, 3.5mm microphone enter discovered a brand new function as an audio output,” Scandurra provides, an enlargement which works alongside the on-board amplified speaker, “whereas a USB [Type]-C port uncovered via a easy adapter allows MIDI-out performance.”
Extra data on Scandurra’s construct is offered on his weblog, whereas supply code and a schematic for an amplifier ought to one be required may be discovered on GitHub below the permissive MIT license.