// 1. generate tones on a speaker on pin 5
// 2. demonstrate functional abstraction
// 3. demonstrate MIDI notes and equal temperament scales
// 4. demonstrate for loop with multiple expressions
// 5. demonstate global constants with 'const float' and 'const int'

const int SPEAKER_PIN = 5;

void setup()
{
  Serial.begin(115200);
}

void loop()
{
  arpeggio(60, 3, 4);  // 60 is the MIDI number for note C4
  silence();
  arpeggio(60, 3, 8);
  arpeggio(85, -6, 8);
  silence();
  silence();
}

void arpeggio(int start, int interval, int length)
{

  for (int note = start, count = 0; count < length; note = note + interval, count = count + 1) {
    float freq = midi_to_freq(note);
    Serial.println(freq);
    tone(SPEAKER_PIN, freq);
    delay(200);
  }
}

const int   MIDI_A0 = 21;
const float freq_A0 = 27.5;
  
float midi_to_freq(int midi_note)
{
  return freq_A0 * pow(2.0, ((float)(midi_note - MIDI_A0)) / 12.0);
}

void silence(void)
{
  noTone(SPEAKER_PIN);
  delay(500);
}