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CircuitPython

README.md

CircuitPython for MTM Computer

Setup

  1. Visit https://circuitpython.org/board/raspberry_pi_pico/ and download the UF2 file for the most recent version of CircuitPython (currently 9.0.5)

  2. Plug MTM Computer module into your PC and Put the MTM Computer in RPI-RP2 UF2 bootloader mode (e.g. hold BOOTSEL button under main knob + RESET button then release BOOTSEL)

  3. Drag CircuitPython UF2 file to the RPI-RP2 drive.
    Your computer may indicate a write error, this is normal with UF2 bootloading

  4. Wait a few seconds and a CIRCUITPY drive will appear on your desktop

  5. Copy the mtm_computer.py file to the CIRCUITPY drive.

  6. Copy one of the demo *_demo_code.py files to CIRCUITPY drive. Rename it code.py.

  7. Open up a serial terminal to the CircuitPython REPL (using Mu, Thonny, tio, screen) to see the output of the demo

Demos

  • leds_demo_code.py -- Simple chase pattern on the six LEDs

  • knob_demo_code.py -- Read all mux inputs (knobs, switch, CVs ins), and mirror them on the LEDs, X-knob and Y-knob send out CV too

  • two_cv_sines_code.py -- Output two sine waves on CV 1 and CV 2, controllable with knobs & switch

Implmentation notes

  • The structure of the library as it stands copies from the SimpleMidi_0.1.ino Arduino sketch by Tom.

  • There is a computer.update() method that should be called regularly to update the state of the mux-based inputs.

  • Audio out via the SPI DAC is not currently supported in CircuitPython. (CircuitPython supports I2S, PWM, and built-in DACs, but not this SPI DAC) But I believe analog CV values can be output since the DAC jacks are DC-coupled.

  • The LEDs in the library are currently set up as PWM, so their brightness can be varied. This may be revisted if we run out of PWM resources.

  • An easy way to put the Computer into UF2 mode without pulling off the knob is to paste this into the REPL:

    import microcontroller 
microcontroller.on_next_reset(microcontroller.RunMode.BOOTLOADER)
microcontroller.reset()

  • And to save the UF2 of the entire CircuitPython setup, do: picotool save -r 0x10000000 0x10200000 my_app.uf2 Note that this saves only the first 2MB of the 16MB flash. This should be fine unles you're storing lots of WAV files or other assets.