Alternate firmware for genMDM devices to work as a Port 2 Serial cable for rhargreaves/mega-drive-midi-interface without Hairless MIDI Bridge

genmdm-alt-usb-midi.ino

#include <SoftwareSerial.h>
#include "MIDIUSB.h"

SoftwareSerial softSerial(11, 2);

byte incomingDinMidiMessage[3];
byte incomingUsbMidiMessage[3];

void setup() {
  Serial1.begin(31250);
  softSerial.begin(4800);
}

void sendBytes(byte message[]) {
  softSerial.write(message, 3);
}

void loop() {
  if (Serial1.available()) {
    Serial1.readBytes(incomingDinMidiMessage, 3);
    sendBytes(incomingDinMidiMessage);
  }

  midiEventPacket_t rx;
  do {
    rx = MidiUSB.read();

    if (rx.header != 0) {
      incomingUsbMidiMessage[0] = rx.byte1;
      incomingUsbMidiMessage[1] = rx.byte2;
      incomingUsbMidiMessage[2] = rx.byte3;
      
      sendBytes(incomingUsbMidiMessage);
    }
  } while (rx.header != 0);
}