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 (taken high, then low) to indicate that the bit is available.

Note: if you’re interfacing with a device that’s clocked by rising edges, you’ll need to make sure that the clock pin is low before the call to shiftOut(), e.g. with a call to digitalWrite(clockPin, LOW).

This is a software implementation; see also the SPI library, which provides a hardware implementation that is faster but works only on specific pins.



shiftOut(dataPin, clockPin, bitOrder, value)



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)






The dataPin and clockPin must already be configured as outputs by a call to 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));




Tutorial for using a shift register.


See also


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