Different ways of using a 75HC595 on an Arduino.

75HC595_option_1

int SER_Pin = 9;   //pin 14 on the 75HC595
int RCLK_Pin = 10;  //pin 12 on the 75HC595
int SRCLK_Pin = 11; //pin 11 on the 75HC595

//How many of the shift registers - change this
#define number_of_74hc595s 2

//do not touch
#define numOfRegisterPins number_of_74hc595s * 8

boolean registers[numOfRegisterPins];

void setup(){
  pinMode(SER_Pin, OUTPUT);
  pinMode(RCLK_Pin, OUTPUT);
  pinMode(SRCLK_Pin, OUTPUT);

  //reset all register pins
  clearRegisters();
  writeRegisters();
}               

//set all register pins to LOW
void clearRegisters(){
  for(int i = numOfRegisterPins - 1; i >=  0; i--){
     registers[i] = LOW;
  }
} 

//Set and display registers
//Only call AFTER all values are set how you would like (slow otherwise)
void writeRegisters(){

  digitalWrite(RCLK_Pin, LOW);

  for(int i = numOfRegisterPins - 1; i >=  0; i--){
    digitalWrite(SRCLK_Pin, LOW);

    int val = registers[i];

    digitalWrite(SER_Pin, val);
    digitalWrite(SRCLK_Pin, HIGH);

  }
  digitalWrite(RCLK_Pin, HIGH);

}

//set an individual pin HIGH or LOW
void setRegisterPin(int index, int value){
  registers[index] = value;
}

void loop(){
  for( int i=0; i<numOfRegisterPins;i++)
  {
    registers[i] = HIGH;
    writeRegisters();
    delay(100);
  }
  clearRegisters();
  writeRegisters();
}