Example Code for Shift Register

ShfitRegister.ino

// Pin Definitions
// The 74HC595 uses a serial communication link which has three pins
#define PIN_DATA 2
#define PIN_CLOCK 3
#define PIN_LATCH 4
int data = 2; 
int clock = 3;
int latch = 4;   

void setup() {
  pinMode(PIN_DATA, OUTPUT);
  pinMode(PIN_CLOCK, OUTPUT);  
  pinMode(PIN_LATCH, OUTPUT);  
}

void loop() {
  for(int i = 0; i < 256; i++) {
   updateLEDsLong(i);
   delay(100); 
  }
}

/*
 * updateLEDs() - sends the LED states set in ledStates to the 74HC595
 * sequence
 */
void updateLEDs(int value){
  digitalWrite(PIN_LATCH, LOW);     // Pulls the chips latch low
  //Shifts out the 8 bits to the shift register
  // MSBFIRST means Most Significant Bit first
  shiftOut(PIN_DATA, PIN_CLOCK, MSBFIRST, value);
  digitalWrite(PIN_LATCH, HIGH);   // Pulls the latch high displaying the data
}

/*
 * updateLEDsLong() - sends the LED states set in ledStates to the 74HC595
 * sequence. Same as updateLEDs except the shifting out is done in software
 * so you can see what is happening.
 */ 
void updateLEDsLong(int value) {
  digitalWrite(PIN_LATCH, LOW);    //Pulls the chips latch low
  int mask = B10000000;
  for (int i = 0; i < 8; i++) {
    // Send one bit of data
    boolean state = ((value & mask) > 0);
    digitalWrite(PIN_DATA, state ? HIGH : LOW);
    // Pulse the CLOCK pin so that the shift register receives the bit of data
    digitalWrite(PIN_CLOCK, HIGH);
    delay(1);
    digitalWrite(PIN_CLOCK, LOW);
    mask >>= 1;
  }
  digitalWrite(latch, HIGH);  //pulls the latch high shifting our data into being displayed
}