What is it?

A simple Raspberry Pi Pico RP2040 / Pico 2 RP2350-based synth to experiment with synthio.

This is a partially-assembled PCB with the 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

The completely assembled SMD sections of the board are:

• TRS MIDI input circuit
• TRS MIDI output circuit
• Capsense touch circuit

The parts you need to add (and solder down) are:

• Raspberry Pi Pico (NOTE: this is the "picotestsynth2" board; it works with Pico1 & Pico2)
• PCM5102 I2S Stereo DAC (more info here)
• 0.91" I2C OLED display (w/ pins in Gnd/Vcc/SCL/SDA order)
• Two 10k potentiometers, 9mm (example pots and knobs)
• One tact switch, 6mm (example switch)
• Headers and sockets to mount Pico & display, to taste
  • This male & female header kit looks pretty good, as I prefer to put female headers on the PCB and male headers on the QTPy and OLED display. You may need to trim down your headers to be the right size
• Feet. I like M2.5 nylon standoffs (e.g. M2.5 standoff asst kit) but feel free to do what you like, including printing an enclosure!

Differences between pico_test_synth2 & pico_test_synth:

• Both use the same components
• Both run the same code
• Both fit in the same enclosure
• pico_test_synth2 drawn in Kicad, pico_test_synth drawn in Eagle
• pico_test_synth2 has square buttons, pico_test_synth has round buttons
• pico_test_synth2 works with Pico2 and Pico1
• pico_test_synth can only work with Pico1

Why did you make it?

I wanted a quick and easy platform to test out CircuitPython's synthio and also play with Mozzi.

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

Some programs written specifically for this board:

• TBish - a TB303-like synth demo (video demo)
• monosynth1 - a full Moog-like monosynth written in Arduino & Mozzi
• hwtest - test out the hardware with a simple synth (video demo)

More code specific for this board coming!

What makes it special?

There aren't that many Pico-based boards that have an I2S audio output, touch inputs and a display. This board does that.