.. _lang-shiftout: shiftOut() ========== Description ----------- Shifts out a byte of data one bit at a time. Starts from either the most (i.e. the leftmost) or least (rightmost) significant bit. Each bit is written in turn to a data pin, after which a clock pin is pulsed to indicate that the bit is available. This is a software implementation; Arduino (as of 0019) also provides an `SPI library <http://arduino.cc/en/Reference/SPI>`_ that uses the hardware implementation. Syntax ------ shiftOut(dataPin, clockPin, bitOrder, value) Parameters ---------- dataPin: the pin on which to output each bit (*int*) clockPin: the pin to toggle once the **dataPin** has been set to the correct value (*int*) bitOrder: which order to shift out the bits; either **MSBFIRST** or **LSBFIRST**. (Most Significant Bit First, or, Least Significant Bit First) value: the data to shift out. (*byte*) Returns ------- None Note ---- The **dataPin** and **clockPin** must already be configured as outputs by a call to `pinMode <http://arduino.cc/en/Reference/PinMode>`_\ (). **shiftOut** is currently written to output 1 byte (8 bits) so it requires a two step operation to output values larger than 255. :: // Do this for MSBFIRST serial int data = 500; // shift out highbyte shiftOut(dataPin, clock, MSBFIRST, (data >> 8)); // shift out lowbyte shiftOut(data, clock, MSBFIRST, data); // Or do this for LSBFIRST serial data = 500; // shift out lowbyte shiftOut(dataPin, clock, LSBFIRST, data); // shift out highbyte shiftOut(dataPin, clock, LSBFIRST, (data >> 8)); Example ------- *For accompanying circuit, see the `tutorial on controlling a 74HC595 shift register <http://arduino.cc/en/Tutorial/ShiftOut>`_.* :: //**************************************************************// // Name : shiftOutCode, Hello World // // Author : Carlyn Maw,Tom Igoe // // Date : 25 Oct, 2006 // // Version : 1.0 // // Notes : Code for using a 74HC595 Shift Register // // : to count from 0 to 255 // //**************************************************************** //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; void setup() { //set pins to output because they are addressed in the main loop pinMode(latchPin, OUTPUT); pinMode(clockPin, OUTPUT); pinMode(dataPin, OUTPUT); } void loop() { //count up routine for (int j = 0; j < 256; j++) { //ground latchPin and hold low for as long as you are transmitting digitalWrite(latchPin, LOW); shiftOut(dataPin, clockPin, LSBFIRST, j); //return the latch pin high to signal chip that it //no longer needs to listen for information digitalWrite(latchPin, HIGH); delay(1000); } } .. include:: /lang/cc-attribution.txt