Arduino - ShftOut13

Back to ShiftOut Tutorial


  Shift Register Example

  Turning on the outputs of a 74HC595 using an array


 * 74HC595 shift register

 * LEDs attached to each of the outputs of the shift register

//Pin connected to ST_CP of 74HC595
int latchPin = 8;
//Pin connected to SH_CP of 74HC595
int clockPin = 12;
////Pin connected to DS of 74HC595
int dataPin = 11;

//holders for infromation you're going to pass to shifting function
byte data;
byte dataArray[10];

void setup() {

  //set pins to output because they are addressed in the main loop

  pinMode(latchPin, OUTPUT);


  //Binary notation as comment

  dataArray[0] = 0xFF; //0b11111111

  dataArray[1] = 0xFE; //0b11111110

  dataArray[2] = 0xFC; //0b11111100

  dataArray[3] = 0xF8; //0b11111000

  dataArray[4] = 0xF0; //0b11110000

  dataArray[5] = 0xE0; //0b11100000

  dataArray[6] = 0xC0; //0b11000000

  dataArray[7] = 0x80; //0b10000000

  dataArray[8] = 0x00; //0b00000000

  dataArray[9] = 0xE0; //0b11100000

  //function that blinks all the LEDs

  //gets passed the number of blinks and the pause time


void loop() {

  for (int j = 0; j < 10; j++) {

    //load the light sequence you want from array

    data = dataArray[j];

    //ground latchPin and hold low for as long as you are transmitting

    digitalWrite(latchPin, 0);

    //move 'em out

    shiftOut(dataPin, clockPin, data);

    //return the latch pin high to signal chip that it

    //no longer needs to listen for information

    digitalWrite(latchPin, 1);



// the heart of the program
void shiftOut(int myDataPin, int myClockPin, byte myDataOut) {

  // This shifts 8 bits out MSB first,

  //on the rising edge of the clock,

  //clock idles low

  //internal function setup

  int i=0;

  int pinState;

  pinMode(myClockPin, OUTPUT);

  pinMode(myDataPin, OUTPUT);

  //clear everything out just in case to

  //prepare shift register for bit shifting

  digitalWrite(myDataPin, 0);

  digitalWrite(myClockPin, 0);

  //for each bit in the byte myDataOut&#xFFFD;


  //This means that %00000001 or "1" will go through such

  //that it will be pin Q0 that lights.

  for (i=7; i>=0; i--)  {

    digitalWrite(myClockPin, 0);

    //if the value passed to myDataOut and a bitmask result

    // true then... so if we are at i=6 and our value is

    // %11010100 it would the code compares it to %01000000

    // and proceeds to set pinState to 1.

    if ( myDataOut & (1<<i) ) {

      pinState= 1;


    else {

      pinState= 0;


    //Sets the pin to HIGH or LOW depending on pinState

    digitalWrite(myDataPin, pinState);

    //register shifts bits on upstroke of clock pin

    digitalWrite(myClockPin, 1);

    //zero the data pin after shift to prevent bleed through

    digitalWrite(myDataPin, 0);


  //stop shifting

  digitalWrite(myClockPin, 0);

//blinks the whole register based on the number of times you want to
//blink "n" and the pause between them "d"
//starts with a moment of darkness to make sure the first blink
//has its full visual effect.
void blinkAll_2Bytes(int n, int d) {

  digitalWrite(latchPin, 0);

  shiftOut(dataPin, clockPin, 0);

  shiftOut(dataPin, clockPin, 0);

  digitalWrite(latchPin, 1);


  for (int x = 0; x < n; x++) {

    digitalWrite(latchPin, 0);

    shiftOut(dataPin, clockPin, 255);

    shiftOut(dataPin, clockPin, 255);

    digitalWrite(latchPin, 1);


    digitalWrite(latchPin, 0);

    shiftOut(dataPin, clockPin, 0);

    shiftOut(dataPin, clockPin, 0);

    digitalWrite(latchPin, 1);