Implement reading and parsing of MIDI messages

[kevinjwalters]

Is there existing work or a plan to add support for reading and parsing of incoming MIDI message?

I might want to do this in the near future. If no one else is working on it then I could provide a partial implementation of this? Is there any existing code demonstrating a good design pattern for this?

Current implementation:

• Can read MIDI messages from one or more specified channels using receive() method which is non-blocking for USB MIDI
• Each message is a class similar to adafruit_bluefruit_connect
• Notes can also be sent with the same messages using new send() method
• NoteOn, NoteOff, PolyphonicKeyPressure (aftertouch) can be constructed with notes in text form, C4 is middle C, A4 is traditional A above C4 (typicalyl 440Hz ref).
• Decent number of unit tests to ensure parser works.

[ladyada]

i was going to do it but ran out of time, @tannewt suggest do it with it returning objects, not lists of bytes. sorta like how we do it here https://github.com/adafruit/Adafruit_CircuitPython_BluefruitConnect

[kevinjwalters]

Got something working using objects per message type. Will be interesting to see how that scales wrt memory usage but it's ok so far.

>>> while True:
...     msg = midi.read_in_port()
...     if msg is not None:
...         print(msg)
...
...
...
<NoteOn object at 200035f0>
<NoteOff object at 200036b0>
<NoteOn object at 20003e10>
<NoteOff object at 20003ed0>
<NoteOn object at 20004590>
<NoteOff object at 20004650>
<NoteOn object at 20004d20>
<NoteOff object at 20004de0>
<NoteOn object at 20001780>
<NoteOff object at 20001960>
<NoteOn object at 200025c0>
<NoteOff object at 20002660>
<NoteOn object at 20003000>
<NoteOff object at 200030c0>
<NoteOn object at 200038a0>
<NoteOff object at 20003960>
<NoteOn object at 200040a0>
<NoteOff object at 20004160>
<NoteOn object at 20004850>
<NoteOff object at 20004910>
<NoteOn object at 20004f80>
<NoteOff object at 20005040>
<NoteOn object at 20001e30>
<NoteOff object at 20001f10>
<NoteOn object at 200020f0>
<NoteOn object at 20002ac0>
<NoteOff object at 20002b80>
<NoteOn object at 20003340>
<ControlChange object at 20003400>
<ControlChange object at 200034c0>
<NoteOn object at 20003580>
<ControlChange object at 20003640>
<ControlChange object at 20003700>

[ladyada]

nice!

[kevinjwalters]

Still more to do but I've got a basic digital square wave monosynth working with:

• new midi input code
• CPX
• a breadboard with three transistors, eight resistors, three capacitors and a 3.5mm socket
• https://github.com/kevinjwalters/circuitpython-examples/blob/master/cpx/cpx-basic-square-monosynth.py

I just hit some memory issues so I need to look at how much mpy vs py saves in case I've already created a bloated library.

[kevinjwalters]

@jedgarpark in Discord:

@kevinjwalters excellent. We just have CC, PitchBend, NoteOn, and NoteOff at the moment, right? Patch Change would be cool. I don't know if I'll make any controllers with Aftertouch or Channel Pressure, but those could be cool if someone did.

[kevinjwalters]

Have a look at CM messages in particular 123 as this may be what midi controllers with a panic button send.

M-Audio Axiom sends 121 0 immediately followed by 123 0 for a panic.

[tannewt]

This is very cool! One idea we had to save memory is to only parse message types that have been imported. (An import will trigger a registration like the BLE code.) That way others can be ignored.