int ledPin = 13;
float val1, val2;
int x = 0b00000000;
int i = 0;
int analogValue;

void setup() {
  Serial.begin(9600);
  // Set pin 13 as an output
  pinMode(ledPin, OUTPUT);

  // Set pin A0 as an input
  pinMode(A0, INPUT);

  noInterrupts();
  // Set the PWM frequency to 980 Hz
  TCCR3B = (TCCR3B & 0b11111000) | 0x02;

  // Set up Timer 3 with a prescaler of 64
  TCCR3B |= (1 << CS31) | (1 << CS30);
  TIMSK3 |= (1 << TOIE3);
  OCR3A = 249;
  interrupts();
}

void loop() {
  // Wait 2 seconds
  if (x == 256) {
    x = 0;
  }
  analogWrite(ledPin, x);
  val1 = analogRead(A0) * 5.0 / 1023.0 ; // convert to volts
  val2 = analogRead(ledPin) * 5.0 / 1023.0; // convert to volts
  // Serial.print("Voltage across Photocell resistor: ");
  // Serial.print(val1, 3);
  // Serial.println("V");
  // Serial.print("Voltage across LED resistor: ");
  // Serial.print(val2, 3);
  // Serial.println("V");
  // Serial.print("Voltage across Photocell: ");
  // Serial.print(analogRead(A6) * 5.0 / 1023.0, 3);
  // Serial.println("V");
  // Serial.print("Duty Cycle %: ");
  // Serial.print(x * 100 / 255.0);
  // Serial.println("%\n");
  x++;
  delay(2000);
}
ISR(TIMER3_OVF_vect) {
  // Read the analog input from pin A0
  if (i >= 0 && i <= 1000) {
    analogValue = analogRead(A0);
    i++;
    Serial.println(i);
  } else if (i > 1000 && i <= 2000) {
    i++;
  } else {
    i = 0;
  }
}