Teensy4.0を使ってハードウェアのデジタルシンセサイザーを作る

#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>
#include <MIDI.h>

MIDI_CREATE_INSTANCE(HardwareSerial, Serial1, MIDI);

// GUItool: begin automatically generated code
AudioPlayQueue           queueOutR;         //xy=435,337
AudioPlayQueue           queueOutL;         //xy=443,285
AudioOutputI2S           i2s1;           //xy=671,303
AudioConnection          patchCord1(queueOutR, 0, i2s1, 1);
AudioConnection          patchCord2(queueOutL, 0, i2s1, 0);
AudioControlSGTL5000     sgtl5000_1;     //xy=492,404
// GUItool: end automatically generated code

float noteDeltaTable[128];
float noteDeltaFineTable[128];
float phase = 0.0f;
float delta = 0.0f;
float amp = 0.0f;             //  0.0 ~ 1.0
float pitchBendRange = 2.0f;  //  0.0 ~ 24.0
float midiNote = 0.0f;        //  0.0 ~ 127.0
float midiPitchBend = 0.0f;   //  -1.0 ~ +1.0

#define SAMPLERATE 44100.0

int16_t buffer[128 * 2];

void setup() {
  MIDI.begin(MIDI_CHANNEL_OMNI);
  Serial.begin(57600);
  //Serial.println("MIDI Input Test");

  //Serial.begin(9600);
  AudioMemory(40);
  sgtl5000_1.enable();
  sgtl5000_1.volume(0.32);
  pinMode(13,OUTPUT);

  phase = 0;
  delta = 500;

  //  Calculate tables
  for (int i = 0; i < 128; i++)
  {
    double freq = 440.0 * pow(2.0, ((double)(i - 69)) / 12.0);
    noteDeltaTable[i] = (float)(freq / SAMPLERATE);
  }

  for (int i = 0; i < 128; i++)
  {
    double cent = 100.0 * ((double)i) / 128.0;
    noteDeltaFineTable[i] = (float)pow(2.0, cent / 1200.0);
  }
}

void updateBuffer()
{
  for (int i = 0; i < 128; i++) {
    float note = midiNote + midiPitchBend * pitchBendRange;
    int noteInt = (int)note;
    int noteFract = (int)((note - (float)noteInt) * 128.0f);
    delta = noteDeltaTable[noteInt] * noteDeltaFineTable[noteFract]; 
    phase += delta;
    if (phase >= 1.0f) phase -= 2.0f;
    auto sig = phase * amp;
    buffer[i] = buffer[i + 128] = (int16_t)(sig * 32767.0f);
  }

  memcpy(queueOutL.getBuffer(), buffer      , 128 * sizeof(int16_t));
  memcpy(queueOutR.getBuffer(), buffer + 128, 128 * sizeof(int16_t));
  queueOutL.playBuffer();
  queueOutR.playBuffer();
}

void loop() {

  // Audio
  if (queueOutL.available() && queueOutL.available()) {
    updateBuffer();
  }

  // Midi
  while (MIDI.read()) {
    int note, velocity, channel, d1, d2;
    byte type = MIDI.getType();
    switch (type) {
      case midi::NoteOn:
        note = MIDI.getData1();
        velocity = MIDI.getData2();
        channel = MIDI.getChannel();
        if (velocity > 0) {
          midiNote = (float)note;
          Serial.println(String("Note On:  ch=") + channel + ", note=" + note + ", velocity=" + velocity);
        } else {
          Serial.println(String("Note Off: ch=") + channel + ", note=" + note);
        }

        break;
      case midi::NoteOff:
        note = MIDI.getData1();
        velocity = MIDI.getData2();
        channel = MIDI.getChannel();
        //Serial.println(String("Note Off: ch=") + channel + ", note=" + note + ", velocity=" + velocity);
        break;

      case midi::PitchBend:
        {
          int data = (MIDI.getData1() | (MIDI.getData2() << 7)) - 8192;
          //Serial.println(String("Pitchbend=") + data);
          midiPitchBend = ((float)data) / 8192.0f;
        }
        break;

      case midi::ControlChange:
        d1 = MIDI.getData1();
        d2 = MIDI.getData2();
        //Serial.println(String("Control Change:") + d1 + " " + d2);
        if (d1 == 2)
        {
          amp = ((float)d2) / 127.0f;
          amp *= amp;
        }
        break;

      default:
        //d1 = MIDI.getData1();
        //d2 = MIDI.getData2();
        //Serial.println(String("Message, type=") + type + ", data = " + d1 + " " + d2);
        break;
    }
  }
}