bool LED_STATE = true;
volatile int timer = 0;

void setup() {
  pinMode(13, OUTPUT);        //Set the pin to be OUTPUT
  DDRD = B11111111;
  DDRB = B00000011;
  
  cli();                      //stop interrupts for till we make the settings
  /*1. First we reset the control register to amke sure we start with everything disabled.*/
  TCCR1A = 0;                 // Reset entire TCCR1A to 0 
  TCCR1B = 0;                 // Reset entire TCCR1B to 0
 
  /*2. We set the prescalar to the desired value by changing the CS10 CS12 and CS12 bits. */  
  TCCR1B |= B00000100;        //Set CS12 to 1 so we get prescalar 256  
  
  /*3. We enable compare match mode on register A*/
  TIMSK1 |= B00000010;        //Set OCIE1A to 1 so we enable compare match A 
  
  /*4. Set the value of register A to 31250*/
  OCR1A = 62500;             //Finally we set compare register A to this value  
  sei();                     //Enable back the interrupts
}

//With the settings above, this IRS will trigger each 500ms.
ISR(TIMER1_COMPA_vect){
  TCNT1  = 0;                  //First, set the timer back to 0 so it resets for next interrupt
  //LED_STATE = !LED_STATE;      //Invert LED state
  //digitalWrite(13,LED_STATE);  //Write new state to the LED on pin D5
  timer += 1;
}

void loop() {
  // put your main code here, to run repeatedly:
  display(timer, 0, 0);
  if(PINB & (1 << 2)){
    digitalWrite(13,LED_STATE); 
    timer = 0;
  }
}

void display(int value, char base, char blanking){
  //blank();
  int dig10 = 0;
  int dig1 = 0;
  if((base==0)&&(blanking==0)){
    dig10 = value/10;
    dig1 = value%10;
    PORTB = B00000010;
    //delay(100);
    segment(dig1);
    //delay(100);
    //blank();
    //PORTB = B00000001;
    //delay(100);
    //segment(dig10);
    //delay(100);
  }
  else if((base==0)&&(blanking==1)){
    dig10 = value/10;
    dig1 = value%10;
    if(dig10<1){
      PORTB = B00000010;
      segment(dig1);
      delay(1);
    }
    else{
      PORTB = B00000010;
      segment(dig1);
      delay(1);
      blank();
      PORTB = B00000001;
      segment(dig10);
      delay(1);      
    }    
  }
  if((base==1)&&(blanking==0)){
    dig10 = 0;
    dig1 = value;
    PORTB = B00000010;
    segment(dig1);
    delay(1);
    blank();
    PORTB = B00000001;
    segment(dig10);
    delay(1);
  }
  else if((base==1)&&(blanking==1)){
    dig1 = value;
    PORTB = B00000010;
    segment(dig1);
    delay(1);
    //blank();
    //PORTB = B00000001;
    //segment(dig10);
    //delay(1);
  }

}

void segment(int digit){
  switch(digit){
    case 0:
      PORTD = B00111111;
      break;
    case 1:
      PORTD = B00000110;
      break;
    case 2:
      PORTD = B01011011;
      break;
    case 3:
      PORTD = B01001111;
      break;
    case 4:
      PORTD = B01100110;
      break;
    case 5:
      PORTD = B01101101;
      break;
    case 6:
      PORTD = B01111101;
      break;
    case 7:
      PORTD = B00000111;
      break;
    case 8:
      PORTD = B01111111;
      break;
    case 9:
      PORTD = B01101111;
      break;
    case 10:
      PORTD = B01110111;
      break;
    case 11:
      PORTD = B01111100;
      break;
    case 12:
      PORTD = B00111001;
      break;
    case 13:
      PORTD = B01011110;
      break;
    case 14:
      PORTD = B01111001;
      break;
    case 15:
      PORTD = B01110001;
  }
}

void blank(){
  PORTB = B00000000;
  PORTD = B00000000;
}