Laser Harp Arduino Code

laser_harp.ino

/*
 * Laser Harp MIDI Controller
 *
 * Authors: Wei-Luen (Alan) Peng and Oren Shoham
 */

// hex to MIDI note reference: https://www.wavosaur.com/download/midi-note-hex.php
// scale: B5, A5, G5, F5, E5, D5, C5
const int notes[7] = {0x5F, 0x5D, 0x5B, 0x59, 0x58, 0x56, 0x54};
const int startingInputPin = 3;

//
int photoDiodes[7] = {HIGH, HIGH, HIGH, HIGH, HIGH, HIGH, HIGH};
bool noteState[7] = {false, false, false, false, false, false, false};

void setup() {
  // baud rate is 57600 because the serial to MIDI converter software recommends it
  Serial.begin(57600);
}

void loop() {
  for (int i = 0; i < 7; i++) {
    int pin = i + startingInputPin;
    photoDiodes[i] = digitalRead(pin); 
  }

  // uncomment the following line to help debug the photodiode input values
//  printPhotoDiodeValues();

  writeMIDINotes();
}

// print photodiode values for debugging
void printPhotoDiodeValues() {
  for (int i = 0; i < 7; i++) {
    Serial.print("value ");
    Serial.print(i);
    Serial.print(": ");
    Serial.print(photoDiodes[i]);
    if (i != 6) {
      Serial.print(", ");
    } else {
      Serial.println("");
    }
  }
}

// write MIDI notes for each photodiode that is off
// if a photodiode is off, the laser is being blocked by something
void writeMIDINotes() {
  for (int i = 0; i < 7; i++) {
    checkPhotoDiodeState(i);
  }
}

// for each photodiode/note:
//    if the beam is interrupted and the note was off, turn it on
//    if the beam is not interrupted and the note was on, turn it off
void checkPhotoDiodeState(int index) {
  int value = photoDiodes[index];
  int note = notes[index];
  bool noteIsOn = noteState[index];
  
  if (value == LOW && noteIsOn == false) {
    noteState[index] = true;
    playNote(note);
  } else if(value == HIGH && noteIsOn == true) {
    noteState[index] = false;
    silenceNote(note);
  }
}

void playNote(int note) {
  noteOn(0x90, note, 0x45);
}

void silenceNote(int note) {
  noteOn(0x90, note, 0x00);
}

// reference: https://www.arduino.cc/en/Tutorial/Midi
// plays a MIDI note. Doesn't check to see that cmd is greater than 127, or that
// data values are less than 127:
void noteOn(int cmd, int pitch, int velocity) {
  Serial.write(cmd);
  Serial.write(pitch);
  Serial.write(velocity);
}