Thin captouch-based synth platform for Raspberry Pi Pico

Features:

• Raspberry Pi Pico
• PWM Audio out
• TRS-A MIDI In / Out
• USB MIDI In/Out
• 19 RGB LEDs
• 22 touch pads (17 notes, 5 modifiers)
• Low part count: 14 BOM line items, mostly passives
• Completely flat surface (only reverse-mount LEDs, capsense pads)
• 6 mm thick when in minimal enclosure (255 x 42 x 6 mm volume)

There are currently three "applications" for the picotouch_synth board, all are in active development, so check the Release page for latest versions as prebuilt UF2 images.

• picotouch_synth -- a wavetable synth with three different patches (video demo)
• pts_drum_machine -- a drum sample player (video demo)
• hwtest -- simple hardware test of the board

Instead of installing CircuitPython, then installling needed libraries, and finally installing the code you want, you can just copy a UF2 file to the RPI-RP2 bootloader drive!

As a rule, all firmware will be offered as pre-built firmware UF2 images for picotouch_synth. Go to the Releases page and download the UF2 you want. Then, to install:

• Unplug picotouch_synth PCB board from USB
• Unclip PCB from case (see this video on releasing the case)
• Hold BOOT button on Pico while plugging back into USB
• Copy the UF2 file to the RPI-RP2 drive
• When board finishes reflashing, it will reboot

Note: if your Pico has more than the 2 MB standard flash (like the purple "RetroScaler" 16MB USB-C ones), the UF2s will still work but the resulting CIRCUITPY drive only be 1 MB. To get the flash space back, you will need to install CircuitPython and install the code files by hand.

For the Sketching in Hardware conference, the firmware shipped on the boards is in circuitpython/picotouch_synth and the pre-built UF2 firwmare in the Releases section.

There were two different boards handed out:

• micro-USB green Raspberry Pi Picos w/ 2 MB flash
• USB-C purple "RetroScaler" Pico clones w/ 16 MB flash.

Both are formated as 2MB devices so if you have a purple board and want the extra flash space, you'll need to install CircuitPython and the code files by hand.

The keyboard is laid out as top row is modulators (three groups of "sliders") and the bottom row plays notes in a particular scale. The A/B/C buttons select different sounds and the X/Y buttons on the right transpose up/down octaves.