Arduino and Piezo play Jingle Bells

jingle_bells.ino

/* Play JingleBells 
 *  by Mischka 2017 (mischk.neocities.org)
 *  
 *  based on the code from:
 *  https://www.arduino.cc/en/Tutorial/PlayMelody
 *  by D. Cuartielles (clay.shirky@nyu.edu)
 *  
 *  connect piezo to pin 9 and GND on arduino board
 */

// TONES  ==========================================
// Start by defining the relationship between
//       note, period, &  frequency.
#define  c     3830    // 261 Hz
#define  d     3400    // 294 Hz
#define  e     3038    // 329 Hz
#define  f     2864    // 349 Hz
#define  g     2550    // 392 Hz
#define  a     2272    // 440 Hz
#define  b     2028    // 493 Hz
#define  C     1912    // 523 Hz
// Define a special note, 'R', to represent a rest
#define  R     0

// SETUP ============================================
// Set up speaker on a PWM pin (digital 9, 10 or 11)
int speakerOut = 9;


void setup() {
  pinMode(speakerOut, OUTPUT);
}

// MELODY and TIMING  =======================================
//  melody[] is an array of notes, accompanied by beats[],
//  which sets each note's relative length (higher #, longer note)
int melody[] = {  a,  a,  a,  a,  a,   a,  a,  C,  f,  g, a,
                  b, b , b, b, b, a, a, a, a, a, g, g, a, g, C, R};
int beats[]  = { 16, 16, 36,  16,  16,  32, 16, 16, 16, 16, 64,
                 16, 16, 16, 16, 16, 16, 16, 8, 8, 16, 16, 16, 16, 36, 16, 16};
int MAX_COUNT = sizeof(melody) / 2; // Melody length, for looping.

// Set overall tempo
long tempo = 15000;
// Set length of pause between notes
int pause = 1000;
// Loop variable to increase Rest length
int rest_count = 100; //<-BLETCHEROUS HACK; See NOTES

// Initialize core variables
int tone_ = 0;
int beat = 0;
long duration  = 0;

// PLAY TONE  ==============================================
// Pulse the speaker to play a tone for a particular duration
void playTone() {
  long elapsed_time = 0;
  if (tone_ > 0) { // if this isn't a Rest beat, while the tone has
    //  played less long than 'duration', pulse speaker HIGH and LOW
    while (elapsed_time < duration) {

      digitalWrite(speakerOut,HIGH);
      delayMicroseconds(tone_ / 2);

      // DOWN
      digitalWrite(speakerOut, LOW);
      delayMicroseconds(tone_ / 2);

      // Keep track of how long we pulsed
      elapsed_time += (tone_);
    }
  }
  else { // Rest beat; loop times delay
    for (int j = 0; j < rest_count; j++) { // See NOTE on rest_count
      delayMicroseconds(duration);  
    }                                
  }                                
}

// LET THE WILD RUMPUS BEGIN =============================
void loop() {
  // Set up a counter to pull from melody[] and beats[]
  for (int i=0; i<MAX_COUNT; i++) {
    tone_ = melody[i];
    beat = beats[i];

    duration = beat * tempo; // Set up timing

    playTone();
    // A pause between notes...
    delayMicroseconds(pause);

 
  }
}