pico_test_synth

A simple Raspberry Pi Pico RP2040-based synth to experiment with synthio and Mozzi.

video demo

** Available on Tindie **

Features

• PCM5102 I2S DAC footprint for high-quality stereo audio out
• Optoisolated MIDI Input via MIDI TRS-A 3.5mm jack
• MIDI output via MIDI TRS-A 3.5mm jack
• Two pots for controlling parameters
• One switch for controlling parameters
• 16 capsense touch buttons for synth triggering
• USB MIDI in/out of course too
• (NOTE: this board will NOT work with the Pico2, since its RP2350 chip has a hardware error)

Software

Programs written for qtpy_synth will work with this board too with minimal changes.

Some programs written specifically for this board:

• hwtest - test out the hardware with a simple synth
  • video demo
• wavesynth - port of wavesynth for qtpy_synth board with some improvements

More code specific for this board coming!

See also:

• https://github.com/todbot/circuitpython-synthio-tricks
  • Contains many other synthio examples that can work with this synth with minimal changes

Enclosure

As seen in the top photo, there's a very simple 3d-printable enclosure available on Printables. You can snap the PCB in to quickly get started, or use M2.5 screws and nuts to secure the PCB more permanently.

Pins used

The board uses all of the QTPy RP2040 pins:

• board.GP28 - middle button
• board.GP27 - right knob
• board.GP26 - left knob
• board.GP22 - I2S data
• board.GP21 - I2S LR clock
• board.GP20 - I2S bit clock
• board.GP19 - I2C SCL for OLED display
• board.GP18 - I2C SDA for OLED display
• board.GP17 - TRS UART MIDI in
• board.GP16 - TRS UART MIDI out
• board.GP0..board.GP15 -- touch pads 1-16

For more details see hwtest/code.py.

Schematic