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authorMarti Bolivar <mbolivar@mit.edu>2010-10-20 06:46:52 -0400
committerMarti Bolivar <mbolivar@mit.edu>2010-10-20 06:46:52 -0400
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+.. _arduino-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);
+ }
+ }
+
+