#define clock_pin 3
#define mclr_pin 5
#define data_pin 4


//storage variables
boolean clock_toggle=false;
boolean clock_enable=false;

int data_pointer=0;
boolean data_send[22]= {0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};

boolean enable=true;


void setup(){

  //set pins as outputs
  for (int i=0; i <= 13; i++){
      pinMode(i, OUTPUT);
      digitalWrite(i, LOW);
  }


cli();//stop interrupts

//set timer1 interrupt
  TCCR1A = 0;// set entire TCCR1A register to 0
  TCCR1B = 0;// same for TCCR1B
  TCNT1  = 0;//initialize counter value to 0
  // set compare match register for 1hz increments
  OCR1A = 1600;// set Timerclock
  // turn on CTC mode
  TCCR1B |= (1 << WGM12);
  // Set Prescaler
  TCCR1B |= (1 << CS10);
  // enable timer compare interrupt
  TIMSK1 |= (1 << OCIE1A);

sei();//allow interrupts

}//end setup

ISR(TIMER1_COMPA_vect){
  if (enable) {

    if (clock_enable) {

      if (clock_toggle) {

        clock_toggle=false;
        digitalWrite(clock_pin, LOW);
        data_pointer=data_pointer+1;
        if (data_pointer>21) {
          enable=false;
          digitalWrite(clock_pin, LOW);
          digitalWrite(data_pin, LOW);
          digitalWrite(mclr_pin, LOW);
        } else if (data_pointer>=6) {
          pinMode(data_pin, INPUT);
        }

      } else {

        clock_toggle=true;
        if (data_pointer<21) {
          digitalWrite(clock_pin, HIGH);
        }

        if (data_send[data_pointer]) {
          digitalWrite(data_pin, HIGH);
        } else {
          digitalWrite(data_pin, LOW);
        }

      }

    } else {

      pinMode(data_pin, OUTPUT);
      digitalWrite(clock_pin, LOW);
      digitalWrite(data_pin, LOW);
      digitalWrite(mclr_pin, LOW);
      data_pointer=0;
      clock_enable=true;
      clock_toggle=false;

    }

  }

}

void loop(){
  //do other things here
}