pico_test_synth

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:

1. PCM5102 I2S DAC footprint for high-quality stereo audio out
2. Optoisolated MIDI Input via MIDI TRS-A 3.5mm jack
3. MIDI output via MIDI TRS-A 3.5mm jack
4. Two pots for controlling parameters
5. One switch for controlling parameters
6. 16 capsense touch buttons for synth triggering
7. USB MIDI in/out of course too

The completely assembled SMD sections of the board are:

1. TRS MIDI input circuit
2. TRS MIDI output circuit
3. Capsense touch circuit

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

1. Raspberry Pi Pico (NOTE: the "pico_test_synth2" board works with Pico2, but the "pico_test_synth1" board will not)
2. PCM5102 I2S Stereo DAC (more info here)
3. 0.91" I2C OLED display (w/ pins in Gnd/Vcc/SCL/SDA order)
4. Two 10k potentiometers, 9mm (example pots and knobs)
5. One tact switch, 6mm (example switch)
6. Headers and sockets to mount Pico & display, to taste
7. This male & female header kit looks pretty good,
8. as I prefer to put female headers on the PCB and male headers on the QTPy and OLED display.
9. You may need to trim down your headers to be the right size
10. Feet. I like M2.5 nylon standoffs (e.g. M2.5 standoff asst kit)
11. but feel free to do what you like, including printing an enclosure!

Differences between pico_test_synth2 & pico_test_synth:

1. Both use the same components
2. Both run the same code
3. Both fit in the same enclosure
4. pico_test_synth2 drawn in Kicad, pico_test_synth drawn in Eagle
5. pico_test_synth2 has square buttons, pico_test_synth has round buttons
6. pico_test_synth2 works with Pico2 and Pico1
7. 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:

1. TBish - a TB303-like synth demo (video demo)
2. monosynth1 - a full Moog-like monosynth written in Arduino & Mozzi
3. 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.

Demo