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.. highlight:: cpp
.. _lang-shiftout:
shiftOut()
==========
Shift out a byte of data, one bit at a time.
.. contents:: Contents
:local:
Library Documentation
---------------------
.. doxygenfunction:: shiftOut
Discussion
----------
This is a software implementation. There is also a hardware :ref:`SPI
<spi>` library available which will be faster and consume less CPU
cycles than this function.
Note that the ``dataPin`` and ``clockPin`` must already be configured
to :ref:`OUTPUT <lang-constants-output>` mode by a call to
:ref:`pinMode() <lang-pinmode>`.
Also note that since shiftOut() outputs 1 byte (8 bits) at a time, it
requires multiple steps to output values larger than 255.
Examples
--------
To use these examples, replace ``dataPin`` and ``clockPin`` with the
numbers of the pins you want to use::
/* MSBFIRST example */
uint16 data = 500;
// shift out high byte
shiftOut(dataPin, clockPin, MSBFIRST, (data >> 8));
// shift out low byte
shiftOut(dataPin, clockPin, MSBFIRST, data);
/* LSBFIRST serial */
data = 500;
// shift out low byte
shiftOut(dataPin, clockPin, LSBFIRST, data);
// shift out high byte
shiftOut(dataPin, clockPin, LSBFIRST, (data >> 8));
Arduino Tutorial Example
------------------------
This Arduino example runs unmodified on the Maple. 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
|
