usb audio synth thing

sketch.cpp

#include <Audio.h>
#include <MIDI.h>

AudioSynthWaveformSine debugTone;
AudioOutputUSB         audioRet;
AudioConnection        patchCord1 (debugTone, 0, audioRet, 0);
AudioConnection        patchCord2 (debugTone, 0, audioRet, 1);

void setup() {
  AudioMemory(15);
  
  // Serial will be used for debugging messages.
  Serial.begin(9600);

  // Callbacks for note handling.
  usbMIDI.setHandleNoteOff(OnNoteOff);
  usbMIDI.setHandleNoteOn(OnNoteOn);

  debugTone.amplitude(1);
  debugTone.frequency(440);
}


void loop() {
  // Continuously read and handle MIDI messages.
  usbMIDI.read();
}

void OnNoteOn(byte channel, byte note, byte vel) {
  Serial.printf("Note ON: %x // V: %x // C: %x\n", note, vel, channel);

  debugTone.amplitude(1);
  debugTone.frequency(noteToFreq(note));
}

void OnNoteOff(byte channel, byte note, byte vel) {
  Serial.printf("Note OFF: %x // V: %x // C: %x\n", note, vel, channel);

  debugTone.amplitude(0);
}

// Convert MIDI note to tonal freq.
//
// Formula: 440 * 2^( midi_note_val - 69) / 12)
float noteToFreq(byte note) {
  float freq = 440 * pow(2, (float(note - 69) / 12));
  Serial.printf("Note: %x // Freq: %.2fHz\n", note, freq);
  return freq;
}