//Pin connected to ST_CP of 74HC595
int latchPin = 8;
//Pin connected to SH_CP of 74HC595
int clockPin = 12;
////Pin connected to DS of 74HC595
int dataPin = 11;

int digit1 = A0;
int digit2 = A1;
int digit3 = A2;
int digit4 = A3;

int count =0;

void setup() {
  //set pins to output so you can control the shift register
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  
  pinMode(digit1, OUTPUT);
  pinMode(digit2, OUTPUT);
  pinMode(digit3, OUTPUT);
  pinMode(digit4, OUTPUT);

}
void callback()
{
  count++;
}
int c = 0;
void loop() {
  
  for(int i=0; i<50; i++){
  
    displayDigit(extractDigit(count,4));
    digitalWrite(digit1, HIGH);
    digitalWrite(digit2, LOW);
    digitalWrite(digit3, LOW);
    digitalWrite(digit4, LOW);
    delay(5);
    displayDigit(extractDigit(count,3));
    digitalWrite(digit1, LOW);
    digitalWrite(digit2, HIGH);
    digitalWrite(digit3, LOW);
    digitalWrite(digit4, LOW);
    delay(5);
    displayDigit(extractDigit(count,2));
    digitalWrite(digit1, LOW);
    digitalWrite(digit2, LOW);
    digitalWrite(digit3, HIGH);
    digitalWrite(digit4, LOW);
    delay(5);
    displayDigit(extractDigit(count,1));
    digitalWrite(digit1, LOW);
    digitalWrite(digit2, LOW);
    digitalWrite(digit3, LOW);
    digitalWrite(digit4, HIGH);
     delay(5);
  }
  count++;
 
}


void displayDigit(int d){
  char number[10] = {0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F};
   digitalWrite(latchPin, LOW);
    // shift out the bits:
    shiftOut(dataPin, clockPin, MSBFIRST, ~number[d]);  

    //take the latch pin high so the LEDs will light up:
    digitalWrite(latchPin, HIGH);
}

int extractDigit(int V, int P)
{
  return int(V/(pow(10,P-1))) % 10; 
}