Add support for MIDI devices

[neilenns]

Is your feature request related to a problem? Please describe.
There are lots of midi devices out there that are essentially big boxes of buttons, encoders, and switches. The new Joystick feature laid the foundation for supporting devices like this. A couple of people have asked for MIDI support in the Discord now.

Describe the solution you'd like

Buttons/encoders/etc. on midi devices show up as inputs in MobiFlight
LEDs on midi devices show up as outputs in MobiFlight (is that even possible?)

Additional context

Here's a C# library that looks useful: https://melanchall.github.io/drywetmidi/articles/devices/Overview.html

[Koseng]

The MIDI stuff seems to be pretty simple.

Midiconnetion code for X-Touch-Mini-FS2020 in python:
https://github.com/maartentamboer/X-Touch-Mini-FS2020/blob/main/midiconnection.py

You get MIDI Messages from the device:

• “Note On Event”-Message for Button pressed
• “Note Off Event”-Message for Button released
• “Control Change”-Message for moving or turning fader or encoder.

[Koseng]

Output from X-Touch-Mini-FS2020 Application:

Startup:

Midi input devices: ['X-TOUCH MINI 0']
Midi output devices: ['Microsoft GS Wavetable Synth 0', 'X-TOUCH MINI 1']
Using midi input device: X-TOUCH MINI 0
Using midi output device: X-TOUCH MINI 1 

Button pressed and released:

note_on channel=10 note=15 velocity=127 time=0  (Button with ID 15 is pressed down. velocity just max value)
note_off channel=10 note=15 velocity=0 time=0  (Button with ID 15 is released. velocity just min value)

Encoder turned. Encoder configured in relative, endless mode:
Value range is 0..127. In relative mode 64 is basically neutral.

control_change channel=10 control=7 value=65 time=0   (Encoder with ID 10 was turned right one increment value for right 65)
control_change channel=10 control=7 value=65 time=0   (Encoder with ID 10 was turned right one increment value for right 65)
control_change channel=10 control=7 value=65 time=0   (Encoder with ID 10 was turned right one increment value for right 65)
control_change channel=10 control=7 value=63 time=0   (Encoder with ID 10 was turned left one increment value for left 63)
control_change channel=10 control=7 value=63 time=0   (Encoder with ID 10 was turned left one increment value for left 63)
=> If the encoder is turned faster, the values for “right” increase and the values for “left” decrease e.g.
control_change channel=10 control=7 value=59 time=0  (turn left)
control_change channel=10 control=7 value=59 time=0   (turn left)
control_change channel=10 control=7 value=67 time=0  (turn right)
control_change channel=10 control=7 value=67 time=0  (turn right)

Fader. The fader has values from 0 to 127:
When moving fader:

control_change channel=10 control=9 value=67 time=0
control_change channel=10 control=9 value=66 time=0
control_change channel=10 control=9 value=65 time=0
control_change channel=10 control=9 value=64 time=0
control_change channel=10 control=9 value=63 time=0
control_change channel=10 control=9 value=62 time=0
control_change channel=10 control=9 value=61 time=0
control_change channel=10 control=9 value=60 time=0
control_change channel=10 control=9 value=59 time=0

[Koseng]

Some Midi Spec:
https://www.midi.org/specifications-old/item/table-2-expanded-messages-list-status-bytes
https://www.midi.org/specifications-old/item/table-1-summary-of-midi-message

---

This is what I like best by far for a possible MobiFlight use case:
https://github.com/codewitch-honey-crisis/MidiSlicer

• Very well documented (linked article at codeproject)
• Very lightweight (library is just the "Midi" Project)
• Many examples (Receiving messages "MidiMonitor" Project)
• MIT license

[neilenns]

This was completed with #561

[jcallano]

There are SysEx messages on the MIDI protocol, enabling fast bidirectional information exchange. Can the feasibility of implementation be assessed?

[neilenns]

Mobiflight already supports MIDI devices. Are you asking for something else?

[jcallano]

System Exclusive (SysEx) messages are special types of MIDI messages that are used to send data that only makes sense to a unit of a certain make and type. This type of messages can be implemented in a way that enable fast bidirectional information exchange of LVARS in chunks of bytes with microcontrollers configured as USB MIDI device like arduino pro micro, arduino UNO , arduino mega, esp32-S3 stm32f103, ETC
Acording to configurations files I can see only CC, note on and note off messages are implemented.

[Koseng]

hi, with the currently used library it is not possible. The library does not properly support SysEx messages. I have another library in mind for the future, but did not have time to try it, and it currently is no priority.

Also probably doing SysEx via configuration is very hard, since the messages can be so different.

What is your concrete use case?

[Koseng]

Ah ok you want to use midi to transfer flightsim variable values?

[jcallano]

Yes, build sim Hardware using Midi for data exchange