One maker has turned a PicoTouch capacitive board into a wave synthesiser. This #MagPiMonday, Lucy Hattersley channels her inner Kraftwerk.

Tod Kurt is a maker with a love of musical synths and his latest creation is PicoSynth, a MIDI synthesiser based on the PicoTouch board.

PicoTouch is a thin capacitive touch platform, and Tod’s software turns Raspberry Pi Pico into a MIDI synthesiser that he can use to play sounds directly, or connect to another computer to control audio software.

The PicoTouch CapSense MIDI keyboard is a slim plastic board with 22 touch pads and 19 RGB LEDs. “It’s one of the thinnest MIDI controllers at about 6 millimetres when Raspberry Pi Pico is installed,” says Tod. 

The ten pads on the bottom are note triggers for the C major scale, while the two pads on the right shift the octave up and down. The top row of pads controls wave and filter functions. Finally, three ‘patch select’ buttons on the right move between different waveforms. You can pick the board up from Tindie for $11, although it will need a Raspberry Pi Pico soldering inside.

“It’s not too bad!” says Tod. “It’s a pretty easy first-time, surface-mount device soldering project.” Tod has created a video showing how to solder Pico to the board.

There is also a PicoTouch Slidercase that is “a simple 3D-printable protective enclosure for the PicoTouch USB MIDI / HID controller board.”

“The result is still very thin and helps prevent false triggers or bad calibration if touching the back on power up,” explains Tod. You print it in two pieces, and no supports are required. Snap the top piece around the PicoTouch board, then slide the combo into the bottom piece. A third ‘picocap’ piece can be printed and glued to the top piece to protect the Pico.

The PicoTouch Synth software is installed on Pico as a ready-made U2F file. The source code is also available.

MIDI sound

Once up and running, PicoSynth is powered by a USB-C socket on the right, and to the left sit three 3.5 mm audio jack connections that provide audio out, MIDI in, and MIDI out. The device can be connected directly via USB-C to a computer running audio software, such as Ableton. You can also use Reaper if you want something that works natively on Raspberry Pi. The USB-C connection to Raspberry Pi Pico provides power and a MIDI connection in one step. This enables you to use the PicoTouch to play instruments in audio software.

“It’s currently running CircuitPython and talking MIDI to my computer which is running Ableton Live so it can do monophonic and polyphonic stuff; you can even play drums with it if you want to,” says Tod.

“It’s a lot of fun!”

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