draft: false
Name: Simple MIDI
short-description: USB MIDI interface and Computer calibrator.
Language: C++ (Pico SDK + ComputerCard)
Creator: Tom Whitwell, Chris Johnson
Version: "0.7.0"
Status: Released
date-created: 2024-11-30
date-updated: 2026-10-02
license: MIT
contact:
  email: tom@musicthing.co.uk
  website: https://www.musicthing.co.uk/
  social:
    github: https://github.com/TomWhitwell

tags:
  - midi
  - midi-host
  - utility
  - cv
  - gate
  - calibration

summary: |
  Simple MIDI turns the Computer into a two-channel USB MIDI interface over the front USB-C connection. Incoming MIDI notes, pitch bend and CC 42 become calibrated pitch CV, gates and CV; the knobs, switch and inputs are sent back as MIDI CCs. It works as a MIDI device (connected to a computer) or as a MIDI host (connected to a MIDI controller).

  It is also used, with a web page, to calibrate the Computer's precision CV outputs and its audio and CV inputs. The calibration is saved on the Computer and used by other cards.

uf2:
  - path: uf2/simple_midi_2.uf2
    name: Simple MIDI 0.7.0

panel:
  inputs:
    - id: AudioIn1
      name: CC 38
      description: Sent to the host as MIDI CC 38 on channel 1
      type: cv

    - id: AudioIn2
      name: CC 39
      description: Sent to the host as MIDI CC 39 on channel 1
      type: cv

    - id: CVIn1
      name: CC 40
      description: Sent to the host as MIDI CC 40 on channel 1
      type: cv

    - id: CVIn2
      name: CC 41
      description: Sent to the host as MIDI CC 41 on channel 1
      type: cv

  outputs:
    - id: AudioOut1
      name: CH 1 CC 42
      description: MIDI channel 1 CC 42 output as CV, approximately -5V to +5V
      type: cv

    - id: AudioOut2
      name: CH 2 CC 42
      description: MIDI channel 2 CC 42 output as CV, approximately -5V to +5V
      type: cv

    - id: CVOut1
      name: CH 1 Pitch
      description: Calibrated 1V/octave pitch CV for the last held note on MIDI channel 1, with +/-2 semitone pitch bend
      type: cv

    - id: CVOut2
      name: CH 2 Pitch
      description: Calibrated 1V/octave pitch CV for the last held note on MIDI channel 2, with +/-2 semitone pitch bend
      type: cv

    - id: PulseOut1
      name: CH 1 Gate
      description: High while any note is held on MIDI channel 1
      type: pulse

    - id: PulseOut2
      name: CH 2 Gate
      description: High while any note is held on MIDI channel 2
      type: pulse

controls:
  switch:
    up:
      name: CC 37
      description: Sends MIDI CC 37 value 127
    middle:
      name: CC 37
      description: Sends MIDI CC 37 value 64
    down:
      name: CC 37 / Calibrate
      description: Sends MIDI CC 37 value 0. Hold down while pressing Reset/Load to start calibration mode, which is controlled from the calibration web page.

  knobs:
    - main:
        name: CC 34
        description: Sent to the host as MIDI CC 34 on channel 1
      x:
        name: CC 35
        description: Sent to the host as MIDI CC 35 on channel 1
      y:
        name: CC 36
        description: Sent to the host as MIDI CC 36 on channel 1

  leds:
    - display: list
      items:
        - id: LED0
          name: CH 1 CC 42
          description: Brightness shows the channel 1 CC 42 value

        - id: LED1
          name: CH 2 CC 42
          description: Brightness shows the channel 2 CC 42 value

        - id: LED2
          name: CH 1 Pitch
          description: Brightness shows the channel 1 note number

        - id: LED3
          name: CH 2 Pitch
          description: Brightness shows the channel 2 note number

        - id: LED4
          name: CH 1 Gate
          description: On while a note is held on channel 1

        - id: LED5
          name: CH 2 Gate
          description: On while a note is held on channel 2

host:
  usb:
    - name: USB MIDI device
      role: midi
      description: Connected to a computer, appears as "MTMComputer MIDI" for MIDI input and output with a DAW or browser tools
    - name: USB MIDI host
      role: midi-host
      description: Connected to a USB MIDI controller, receives notes, pitch bend and CC 42 from it
  notes: |
    Device or host mode is detected automatically at power-up. Power-cycle the Workshop System, rather than only pressing Reset, when changing what is connected.