USB-MIDI control of GRAINS using MIDI library

EDIT: DISCLAIMER: all firmwares described here are experimental, use at your own risk. There is a possibility that your grains module will be bricked when uploading new firmwares (see this AE Modular forum post for a description of the possible problem and solution: forum.aemodular.com/thread/1858/serialport-show-anymore-brick-grains).

Hi all,
I have a long-term goal of having multiple MIDI-controlled GRAINS be the main signal sources in my rack. My first step is to use the USB connection on GRAINS for sending MIDI to the module. On my computer, I am using ttyMIDI. I tried this out with the MIDI-out firmware on GRAINS, and was able to make that connection successfully, such that sending a MIDI note from my computer resulted in a gate out on GRAINS (I was also able to send CV from GRAINS to my computer as MIDI CC). I noticed that the code for that firmware did not use the MIDI Library.

I very slightly edited the built-in MIDI library callbacks example available in the Arduino IDE to similarly send a gate out from GRAINS when it received a MIDI note from my computer over USB. However, I wasn't able to get a gate out from GRAINS. I wasn't sure if there was an implementation detail of GRAINS that prevented such a use of the vanilla MIDI library, or if I was missing something obvious in my code. It also seems possible that I will need to parse the MIDI messages myself without using a library, like in the MIDI Out firmware, but I figured I would start here. Thanks for your help!


#include <MIDI.h>

#define DIGITAL_OUT_PIN 8

MIDI_CREATE_DEFAULT_INSTANCE();

void handleNoteOn(byte channel, byte pitch, byte velocity)
{
   // Turn digital out high when the note is received.
   digitalWrite(DIGITAL_OUT_PIN, HIGH);
}

void handleNoteOff(byte channel, byte pitch, byte velocity)
{
   // Turn digital out low when the note is released.
   digitalWrite(DIGITAL_OUT_PIN, LOW);
}

// -----------------------------------------------------------------------------

void setup()
{
   pinMode(DIGITAL_OUT_PIN, OUTPUT);
   
   // Connect the handleNoteOn function to the library,
   // so it is called upon reception of a NoteOn.
   MIDI.setHandleNoteOn(handleNoteOn);

   // Do the same for NoteOffs
   MIDI.setHandleNoteOff(handleNoteOff);

   // Initiate MIDI communications, listen to all channels
   MIDI.begin(MIDI_CHANNEL_OMNI);
}

void loop()
{
   // Call MIDI.read the fastest you can for real-time performance.
   MIDI.read();
}