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https://github.com/todbot/qtpy_synth

Hardware & software for a tiny QTPy-driven synth
https://github.com/todbot/qtpy_synth

circuitpython qtpy qtpyrp2040 rp2040 synthdiy synthesizer synthio

Last synced: 2 months ago
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Hardware & software for a tiny QTPy-driven synth

Host: GitHub
URL: https://github.com/todbot/qtpy_synth
Owner: todbot
License: mit
Created: 2023-06-28T21:32:24.000Z (over 1 year ago)
Default Branch: main
Last Pushed: 2024-04-28T00:54:44.000Z (8 months ago)
Last Synced: 2024-09-27T09:23:58.317Z (3 months ago)
Topics: circuitpython, qtpy, qtpyrp2040, rp2040, synthdiy, synthesizer, synthio
Language: Python
Homepage:
Size: 1.61 MB
Stars: 19
Watchers: 5
Forks: 2
Open Issues: 0
Metadata Files:
- Readme: README.md
- License: LICENSE

Awesome Lists containing this project

README

        # qtpy_synth

A simple [QTPy RP2040](https://learn.adafruit.com/adafruit-qt-py-2040/overview)-based

synth to experiment with [`synthio`](https://github.com/todbot/circuitpython-synthio-tricks).





### Features

 - Mono audio output circuit, converting PWM to audio, as per [RP2040 design guidelines](https://datasheets.raspberrypi.com/rp2040/hardware-design-with-rp2040.pdf#page=24)

 - Optoisolated MIDI Input via [MIDI TRS-A 3.5mm jack](https://www.perfectcircuit.com/make-noise-0-coast-midi-cable.html)

 - Two pots for controlling parameters

 - One switch for controlling parameters

 - Four capsense touch buttons for synth triggering

 - USB MIDI in/out of course too

### Software

Some programs written specifically for this board:

- [hwtest](./circuitpython/hwtest/code.py) - test out the hardware with a simple synth

- [simpletouchsynth](./circuitpython/simpletouchsynth) - play with filters using touch sensors. Uses intial cut at a "qtpy_synth" hardware library.

- [dronesynth](./circuitpython/dronesynth) - 8-oscillator drone synth

- [wavesynth](./circuitpython/wavesynth) - larger general two-osc synth that can also do wave-mixing and wavetables. Has many rough edges but can sound great!

  - early video demo:

  

    [![Wavetable synth w/ CircuitPython synthio on QTPy RP2040](http://img.youtube.com/vi/4hgDi6MNfsI/0.jpg)](https://www.youtube.com/watch?v=4hgDi6MNfsI)]

  - another video demo:

  

    [![More Wavetable synth w/ CircuitPython synthio on QTPy RP2040](http://img.youtube.com/vi/80yjwxscnnA/0.jpg)](https://www.youtube.com/watch?v=80yjwxscnnA)]

#### See also:

- https://github.com/todbot/circuitpython-synthio-tricks

  - Contains [many other synthio examples](https://github.com/todbot/circuitpython-synthio-tricks/tree/main/examples) that can work with this synth with minimal changes

### Building it

The [Tindie version is a partially-assembled PCB](https://www.tindie.com/products/todbot/qtpy_synth/). 

The completely assembled SMD sections of the board are:

* audio output circuit

* TRS MIDI input circuit

The parts you need to add are:

* [QTPy RP2040](https://www.adafruit.com/product/4900)

* 0.91" [I2C OLED display](https://amzn.to/3KDmy73) (w/ pins in Gnd/Vcc/SCL/SDA order)

* Two 10k potentiometers, 9mm  ([example pots](https://amzn.to/3DYYJm5)) and [knobs](https://amzn.to/3QAkSyR)

* One tact switch, 6mm ([example switch](https://amzn.to/47nJaSN))

* Headers and sockets to mount QTPy & display, to taste

  * [This male & female header kit looks pretty good](https://amzn.to/3qqbtiO),

    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](https://amzn.to/45qVjFb))

  but feel free to do what you like, including making an enclosure!

* Or [3d-print a simple case](https://www.printables.com/model/757087-case-for-qtpy_synth-circuitpython-synthesizer) for it! I also like these [3d-printed knobs](https://www.thingiverse.com/thing:5759656)

### Pins used

The board uses all of the QTPy RP2040 pins:

* `board.A0` - left knob

* `board.A1` - right knob

* `board.TX` - middle button

* `board.RX` - TRS UART MIDI in

* `board.MOSI` - PWM Audio Out

* `board.SCL` & `board.SDA` - I2C bus for OLED display

* `board.A3`, `board.A2`, `board.MISO`, `board.SCK`,  -- touch pads 1,2,3,4

For more details see [`hwtest/code.py`](https://github.com/todbot/qtpy_synth/tree/main/circuitpython/hwtest/code.py).

### Schematic

[](./schematics/qtpy_synth_proto2b_sch.pdf)