#include "pitches.h"

float noteToFreq(int note) {
  return 220.0 * pow(2.0, note / 12.0);
}

// const int iterFrequency = 62500;
const int iterPeriod = 125;

const uint8_t buzzerPin = 8;
const uint8_t buttonPins[] = { 12, 11, 10, 9, 7, 6, 5, 4 };
const float freqs[] = {
  noteToFreq(3), noteToFreq(5), noteToFreq(7), noteToFreq(8),
  noteToFreq(10), noteToFreq(12), noteToFreq(14), noteToFreq(15)
};

const int numTones = sizeof(buttonPins) / sizeof(buttonPins[0]);

volatile unsigned long iter = 0;
int periods[numTones] = {};

void setup() {
  pinMode(buzzerPin, OUTPUT);

  for (int i = 0; i < numTones; i++) {
    pinMode(buttonPins[i], INPUT_PULLUP);
    periods[i] = round(1e6 / freqs[i] / iterPeriod);
  }

  noInterrupts();
  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = 0;
  OCR1A = 249;
  TCCR1B |= (1 << WGM12);
  TCCR1B |= (1 << CS11);
  TIMSK1 |= (1 << OCIE1A);
  interrupts();
}

void loop() {
  
}

ISR(TIMER1_COMPA_vect) {
  iter++;

  float sum = 0;

  for (int i = 0; i < numTones; i++) {
    if (digitalRead(buttonPins[i]) == LOW) {
      if (iter % periods[i] > round(periods[i] / 2)) {
        sum++;
      } else {
        sum--;
      }
    }
  }

  sum /= (float)numTones;
  sum++;
  sum *= 127.0;

  analogWrite(buzzerPin, sum);
  // if (sum > 0) {
  //   digitalWrite(buzzerPin, HIGH);
  // } else {
  //   digitalWrite(buzzerPin, LOW);
  // }
}