Inventive designer Salvatore “Turi” Scandurra has given a youngsters’s toy keyboard a significant 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 affordable toy musical keyboard,” Scandurra explains of the origins of the Picophonica undertaking. “The sound high quality was atrocious, and it might solely play one word at a time. So I eliminated its circuitry whereas holding its enclosure, speaker, and keybed, and with some tinkering and a Raspberry Pi Pico I turned it into one thing usable.”
Dad and mom, in addition to these with a private curiosity in low-cost plastic tat, shall be accustomed to the fashion of keyboard picked for the undertaking. Whereas technically useful, they’re very a lot a single voice affair — enjoying 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 — a minimum of, any extra. As an alternative, the housing performs host to a Raspberry Pi Pico improvement board and its dual-core Arm Cortex-M0+ RP2040 microcontroller operating 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 improvement board. (📷: Turi Scandurra)
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 offer analog audio output by way of pulse-width modulation (PWM). “The prevailing, relatively pointless, 3.5mm microphone enter discovered a brand new objective as an audio output,” Scandurra provides, an enlargement which works alongside the on-board amplified speaker, “whereas a USB [Type]-C port uncovered by way of a easy adapter allows MIDI-out performance.”
Extra info on Scandurra’s construct is accessible on his weblog, whereas supply code and a schematic for an amplifier ought to one be required will be discovered on GitHub below the permissive MIT license.
