shiftOut() — Maple v0.0.11 Documentation

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# shiftOut()

Shift out a byte of data, one bit at a time.

Contents

- Library Documentation
- Discussion
- Examples
- Arduino Tutorial Example

## Library Documentation

void shiftOut(uint8 dataPin, uint8 clockPin, uint8 bitOrder, uint8 value)

  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:

  - `dataPin` -

    Pin to shift data out on

  - `clockPin` -

    Pin to pulse after each bit is shifted out

  - `bitOrder` -

    Either MSBFIRST (big-endian) or LSBFIRST (little-endian).

  - `value` -

    Value to shift out

## Discussion

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.

## 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.

    //**************************************************************//
    //  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.

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