Shift out a byte of data, one bit at a time.
Shift out a byte of data, one bit at a time.
This function starts at either the most significant or least significant bit in a byte value, and shifts out each byte in order onto a data pin. After each bit is written to the data pin, a separate clock pin is pulsed to indicate that the new bit is available.
Parameters: |
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This is a software implementation. There is also a hardware 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 OUTPUT mode by a call to pinMode().
Also note that since shiftOut() outputs 1 byte (8 bits) at a time, it requires multiple steps to output values larger than 255.
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));
This Arduino example runs unmodified on the Maple. For accompanying circuit, see the tutorial on controlling a 74HC595 shift register.
//**************************************************************//
// 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);
}
}
License and Attribution
Some information in this page was adapted from the Arduino Reference Documentation, which is released under a Creative Commons Attribution-ShareAlike 3.0 License.