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[Docs] added basic midi documention of common features (#13113 )

Co-authored-by: precondition <57645186+precondition@users.noreply.github.com>
Co-authored-by: Ryan <fauxpark@gmail.com>
Co-authored-by: Joel Challis <git@zvecr.com>

2021-06-06 23:53:20 -07:00

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MIDI

Usage

First, enable MIDI by adding the following to your rules.mk:

MIDI_ENABLE = yes

There are two MIDI systems in QMK: basic and advanced. With basic MIDI you will only be able to send Note On and Note Off messages using the note keycodes, meaning that keycodes like MI_OCTU and MI_OCTD will not work. Advanced MIDI allows you to do things like octave shifts, channel changes, velocity changes, modulation, and more.

Basic MIDI

To enable basic MIDI, add the following to your config.h:

#define MIDI_BASIC

Advanced MIDI

To enable advanced MIDI, add the following to your config.h:

#define MIDI_ADVANCED

Sending Control Change (CC) Messages

If you're aiming to emulate the features of something like a Launchpad or other MIDI controller you'll need to access the internal MIDI device directly.

Because there are so many possible CC messages, not all of them are implemented as keycodes. Additionally, you might need to provide more than just two values that you would get from a keycode (pressed and released) - for example, the analog values from a fader or a potentiometer. So, you will need to implement custom keycodes if you want to use them in your keymap directly using process_record_user().

For reference of all the possible control code numbers see MIDI Specification

Example code for using Generic On Off Switches as per MIDI Specification.

#include QMK_KEYBOARD_H

extern MidiDevice midi_device;

// MIDI CC codes for generic on/off switches (80, 81, 82, 83)
// Off: 0-63
// On:  64-127

#define MIDI_CC_OFF 0
#define MIDI_CC_ON  127

enum custom_keycodes {
    MIDI_CC80 = SAFE_RANGE,
};

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
    switch (keycode) {
        case MIDI_CC80:
            if (record->event.pressed) {
                midi_send_cc(&midi_device, midi_config.channel, 80, ON);
            } else {
                midi_send_cc(&midi_device, midi_config.channel, 80, OFF);
            }
            return true;
    }
    return true;
};

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
    LAYOUT(
        // ...
        MIDI_CC80,
        // ...
    )
};

Keycodes

Keycode	Aliases	Description
`MI_ON`		Turn MIDI on
`MI_OFF`		Turn MIDI off
`MI_TOG`		Toggle MIDI enabled
`MI_C`		C octave 0
`MI_Cs`	`MI_Db`	C♯/D♭ octave 0
`MI_D`		D octave 0
`MI_Ds`	`MI_Eb`	D♯/E♭ octave 0
`MI_E`		E octave 0
`MI_F`		F octave 0
`MI_Fs`	`MI_Gb`	F♯/G♭ octave 0
`MI_G`		G octave 0
`MI_Gs`	`MI_Gs`	G♯/A♭ octave 0
`MI_A`		A octave 0
`MI_As`	`MI_Bb`	A♯/B♭ octave 0
`MI_B`		B octave 0
`MI_C_1`		C octave 1
`MI_Cs_1`	`MI_Db_1`	C♯/D♭ octave 1
`MI_D_1`		D octave 1
`MI_Ds_1`	`MI_Eb_1`	D♯/E♭ octave 1
`MI_E_1`		E octave 1
`MI_F_1`		F octave 1
`MI_Fs_1`	`MI_Gb_1`	F♯/G♭ octave 1
`MI_G_1`		G octave 1
`MI_Gs_1`	`MI_Ab_1`	G♯/A♭ octave 1
`MI_A_1`		A octave 1
`MI_As_1`	`MI_Bb_1`	A♯/B♭ octave 1
`MI_B_1`		B octave 1
`MI_C_2`		C octave 2
`MI_Cs_2`	`MI_Db_2`	C♯/D♭ octave 2
`MI_D_2`		D octave 2
`MI_Ds_2`	`MI_Eb_2`	D♯/E♭ octave 2
`MI_E_2`		E octave 2
`MI_F_2`		F octave 2
`MI_Fs_2`	`MI_Gb_2`	F♯/G♭ octave 2
`MI_G_2`		G octave 2
`MI_Gs_2`	`MI_Ab_2`	G♯/A♭ octave 2
`MI_A_2`		A octave 2
`MI_As_2`	`MI_Bb_2`	A♯/B♭ octave 2
`MI_B_2`		B octave 2
`MI_C_3`		C octave 3
`MI_Cs_3`	`MI_Db_3`	C♯/D♭ octave 3
`MI_D_3`		D octave 3
`MI_Ds_3`	`MI_Eb_3`	D♯/E♭ octave 3
`MI_E_3`		E octave 3
`MI_F_3`		F octave 3
`MI_Fs_3`	`MI_Gb_3`	F♯/G♭ octave 3
`MI_G_3`		G octave 3
`MI_Gs_3`	`MI_Ab_3`	G♯/A♭ octave 3
`MI_A_3`		A octave 3
`MI_As_3`	`MI_Bb_3`	A♯/B♭ octave 3
`MI_B_3`		B octave 3
`MI_C_4`		C octave 4
`MI_Cs_4`	`MI_Db_4`	C♯/D♭ octave 4
`MI_D_4`		D octave 4
`MI_Ds_4`	`MI_Eb_4`	D♯/E♭ octave 4
`MI_E_4`		E octave 4
`MI_F_4`		F octave 4
`MI_Fs_4`	`MI_Gb_4`	F♯/G♭ octave 4
`MI_G_4`		G octave 4
`MI_Gs_4`	`MI_Ab_4`	G♯/A♭ octave 4
`MI_A_4`		A octave 4
`MI_As_4`	`MI_Bb_4`	A♯/B♭ octave 4
`MI_B_4`		B octave 4
`MI_C_5`		C octave 5
`MI_Cs_5`	`MI_Db_5`	C♯/D♭ octave 5
`MI_D_5`		D octave 5
`MI_Ds_5`	`MI_Eb_5`	D♯/E♭ octave 5
`MI_E_5`		E octave 5
`MI_F_5`		F octave 5
`MI_Fs_5`	`MI_Gb_5`	F♯/G♭ octave 5
`MI_G_5`		G octave 5
`MI_Gs_5`	`MI_Ab_5`	G♯/A♭ octave 5
`MI_A_5`		A octave 5
`MI_As_5`	`MI_Bb_5`	A♯/B♭ octave 5
`MI_B_5`		B octave 5
`MI_OCT_N2`		Set octave to -2
`MI_OCT_N1`		Set octave to -1
`MI_OCT_0`		Set octave to 0
`MI_OCT_1`		Set octave to 1
`MI_OCT_2`		Set octave to 2
`MI_OCT_3`		Set octave to 3
`MI_OCT_4`		Set octave to 4
`MI_OCT_5`		Set octave to 5
`MI_OCT_6`		Set octave to 6
`MI_OCT_7`		Set octave to 7
`MI_OCTD`		Move down an octave
`MI_OCTU`		Move up an octave
`MI_TRNS_N6`		Set transposition to -6 semitones
`MI_TRNS_N5`		Set transposition to -5 semitones
`MI_TRNS_N4`		Set transposition to -4 semitones
`MI_TRNS_N3`		Set transposition to -3 semitones
`MI_TRNS_N2`		Set transposition to -2 semitones
`MI_TRNS_N1`		Set transposition to -1 semitone
`MI_TRNS_0`		No transposition
`MI_TRNS_1`		Set transposition to +1 semitone
`MI_TRNS_2`		Set transposition to +2 semitones
`MI_TRNS_3`		Set transposition to +3 semitones
`MI_TRNS_4`		Set transposition to +4 semitones
`MI_TRNS_5`		Set transposition to +5 semitones
`MI_TRNS_6`		Set transposition to +6 semitones
`MI_TRNSD`		Decrease transposition
`MI_TRNSU`		Increase transposition
`MI_VEL_0`		Set velocity to 0
`MI_VEL_1`		Set velocity to 12
`MI_VEL_2`		Set velocity to 25
`MI_VEL_3`		Set velocity to 38
`MI_VEL_4`		Set velocity to 51
`MI_VEL_5`		Set velocity to 64
`MI_VEL_6`		Set velocity to 76
`MI_VEL_7`		Set velocity to 89
`MI_VEL_8`		Set velocity to 102
`MI_VEL_9`		Set velocity to 114
`MI_VEL_10`		Set velocity to 127
`MI_VELD`		Decrease velocity
`MI_VELU`		Increase velocity
`MI_CH1`		Set channel to 1
`MI_CH2`		Set channel to 2
`MI_CH3`		Set channel to 3
`MI_CH4`		Set channel to 4
`MI_CH5`		Set channel to 5
`MI_CH6`		Set channel to 6
`MI_CH7`		Set channel to 7
`MI_CH8`		Set channel to 8
`MI_CH9`		Set channel to 9
`MI_CH10`		Set channel to 10
`MI_CH11`		Set channel to 11
`MI_CH12`		Set channel to 12
`MI_CH13`		Set channel to 13
`MI_CH14`		Set channel to 14
`MI_CH15`		Set channel to 15
`MI_CH16`		Set channel to 16
`MI_CHD`		Decrease channel
`MI_CHU`		Increase channel
`MI_ALLOFF`		Stop all notes
`MI_SUS`		Sustain
`MI_PORT`		Portmento
`MI_SOST`		Sostenuto
`MI_SOFT`		Soft Pedal
`MI_LEG`		Legato
`MI_MOD`		Modulation
`MI_MODSD`		Decrease modulation speed
`MI_MODSU`		Increase modulation speed
`MI_BENDD`		Bend pitch down
`MI_BENDU`		Bend pitch up

Configuration

Certain values are stored in the midi_config struct. This configuration is not persisted to EEPROM. By default, these values are:

Configuration	Value	Comments
Octave	`4`	Corresponds to `MI_OCT_2`
Transposition	`0`
Velocity	`127`
Channel	`0`
Modulation Interval	`8`

For the above, the MI_C keycode will produce a C3 (note number 48), and so on.

References

MIDI Specification

QMK C Files

quantum/process_keycode/process_midi.c
quantum/quantum_keycodes.h
tmk_core/protocol/midi.h
tmk_core/protocol/midi.c
tmk_core/protocol/qmk_midi.c
tmk_core/protocol/midi_device.h

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