// Pin ST_CP of HC595, 
// we will be using this pin
// to control led status
// using digitalWrite(latchPin, ledstatus);
int latchPin = 12;

// Pin SH_CP of HC595
int clockPin = 11;

// Pin DS of HC595
int dataPin = 13;

const int HC595_count = 2;  // Number of HC595
byte ledStatus[HC595_count] = {0}; // Array of led status
int i, j; // Variables to use in for loop

void setup() {
  // put your setup code here, to run once:
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
}

void fillValueToLed(byte value){
  for (i = 0; i < HC595_count; i++){
    ledStatus[i] = value;
  }
}

void shiftOut_inShorten(){
  digitalWrite(latchPin, LOW);
  for (i = 0; i < HC595_count; i++){
    shiftOut(dataPin, clockPin, MSBFIRST, ledStatus[i]);
  }
  digitalWrite(latchPin, HIGH);
  delay(1000);
};

void loop() {
  // put your main code here, to run repeatedly:
  //Using MSBFIRST - the light turn in correct order
  //Using LSBFIRST - the light turn in reverse order
  fillValueToLed(0b10101010);
  shiftOut_inShorten();
  
  fillValueToLed(0b01010101);
  shiftOut_inShorten();
}