// segment pin definitions
#define SegA   12
#define SegB   11
#define SegC   10
#define SegD    9
#define SegE    8
#define SegF    7
#define SegG    6

// common pins of the four digits definitions
#define Dig1    5
#define Dig2    4
#define Dig3    3
#define Dig4    2

volatile int NUMBER = 1;
volatile int current_digit;

void setup() {
  // put your setup code here, to run once:
  pinMode(SegA, OUTPUT);
  pinMode(SegB, OUTPUT);
  pinMode(SegC, OUTPUT);
  pinMode(SegD, OUTPUT);
  pinMode(SegE, OUTPUT);
  pinMode(SegF, OUTPUT);
  pinMode(SegG, OUTPUT);
  pinMode(Dig1, OUTPUT);
  pinMode(Dig2, OUTPUT);
  pinMode(Dig3, OUTPUT);
  pinMode(Dig4, OUTPUT);

  current_digit = 1;

  cli();
  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = 0;
  OCR1A = 2048;                       // compare match register 16MHz/1024/125Hz
  TCCR1B |= (1 << WGM12);               // CTC mode
  TCCR1B |= (1 << CS12) | (1 << CS10);  // 1024 prescaler
  TIMSK1 |= (1 << OCIE1A);              // enable timer compare interrupt
  sei();

}

void loop() {
  // put your main code here, to run repeatedly:

}

void setDigit(int i) {
  for (int j = Dig4; j <= Dig1; j++)
    digitalWrite(j, LOW);
  digitalWrite(i, HIGH);
}

ISR(TIMER1_COMPA_vect) {
  setDigit(6 - current_digit);
    switch (current_digit)
    {
      case 1:
        disp(NUMBER / 1000);   // prepare to display digit 1 (most left)
        break;
      case 2:
        disp( (NUMBER / 100) % 10);   // prepare to display digit 2
        break;
      case 3:
        disp( (NUMBER / 10) % 10);   // prepare to display digit 3
        break;
      case 4:
        disp(NUMBER % 10);   // prepare to display digit 4 (most right)
    }
    current_digit++;
  if (current_digit % 5 == 0) {
    NUMBER++;
    current_digit = 1;
  }
  

}

// void dispNumber(int number) {
//     int lastDigitIO=2;
//     while(number>0&&number<=9999) {
//     digitalWrite(lastDigitIO, HIGH);
//     disp(number%10);
//     number=(number-number%10)/10;
//     lastDigitIO++;
//     }

// }

void disp(byte number)
{
  switch (number)
  {
    case 0:  // print 0
      digitalWrite(SegA, LOW);
      digitalWrite(SegB, LOW);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, LOW);
      digitalWrite(SegE, LOW);
      digitalWrite(SegF, LOW);
      digitalWrite(SegG, HIGH);
      break;

    case 1:  // print 1
      digitalWrite(SegA, HIGH);
      digitalWrite(SegB, LOW);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, HIGH);
      digitalWrite(SegE, HIGH);
      digitalWrite(SegF, HIGH);
      digitalWrite(SegG, HIGH);
      break;

    case 2:  // print 2
      digitalWrite(SegA, LOW);
      digitalWrite(SegB, LOW);
      digitalWrite(SegC, HIGH);
      digitalWrite(SegD, LOW);
      digitalWrite(SegE, LOW);
      digitalWrite(SegF, HIGH);
      digitalWrite(SegG, LOW);
      break;

    case 3:  // print 3
      digitalWrite(SegA, LOW);
      digitalWrite(SegB, LOW);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, LOW);
      digitalWrite(SegE, HIGH);
      digitalWrite(SegF, HIGH);
      digitalWrite(SegG, LOW);
      break;

    case 4:  // print 4
      digitalWrite(SegA, HIGH);
      digitalWrite(SegB, LOW);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, HIGH);
      digitalWrite(SegE, HIGH);
      digitalWrite(SegF, LOW);
      digitalWrite(SegG, LOW);
      break;

    case 5:  // print 5
      digitalWrite(SegA, LOW);
      digitalWrite(SegB, HIGH);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, LOW);
      digitalWrite(SegE, HIGH);
      digitalWrite(SegF, LOW);
      digitalWrite(SegG, LOW);
      break;

    case 6:  // print 6
      digitalWrite(SegA, LOW);
      digitalWrite(SegB, HIGH);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, LOW);
      digitalWrite(SegE, LOW);
      digitalWrite(SegF, LOW);
      digitalWrite(SegG, LOW);
      break;

    case 7:  // print 7
      digitalWrite(SegA, LOW);
      digitalWrite(SegB, LOW);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, HIGH);
      digitalWrite(SegE, HIGH);
      digitalWrite(SegF, HIGH);
      digitalWrite(SegG, HIGH);
      break;

    case 8:  // print 8
      digitalWrite(SegA, LOW);
      digitalWrite(SegB, LOW);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, LOW);
      digitalWrite(SegE, LOW);
      digitalWrite(SegF, LOW);
      digitalWrite(SegG, LOW);
      break;

    case 9:  // print 9
      digitalWrite(SegA, LOW);
      digitalWrite(SegB, LOW);
      digitalWrite(SegC, LOW);
      digitalWrite(SegD, LOW);
      digitalWrite(SegE, HIGH);
      digitalWrite(SegF, LOW);
      digitalWrite(SegG, LOW);
  }
}