Learning Examples | Foundations | Hacking | Links
/*
Shift Register Example
for 74HC595 shift register
This sketch turns reads serial input and uses it to set the pins
of a 74HC595 shift register.
Hardware:
* 74HC595 shift register attached to pins 2, 3, and 4 of the Arduino,
as detailed below.
* LEDs attached to each of the outputs of the shift register
Created 22 May 2009
Created 23 Mar 2010
by Tom Igoe
*/
//Pin connected to latch pin (ST_CP) of 74HC595
const int latchPin = 8;
//Pin connected to clock pin (SH_CP) of 74HC595
const int clockPin = 12;
////Pin connected to Data in (DS) of 74HC595
const int dataPin = 11;
void setup() {
//set pins to output because they are addressed in the main loop
pinMode(latchPin, OUTPUT);
pinMode(dataPin, OUTPUT);
pinMode(clockPin, OUTPUT);
Serial.begin(9600);
Serial.println("reset");
}
void loop() {
if (Serial.available() > 0) {
// ASCII '0' through '9' characters are
// represented by the values 48 through 57.
// so if the user types a number from 0 through 9 in ASCII,
// you can subtract 48 to get the actual value:
int bitToSet = Serial.read() - 48;
// write to the shift register with the correct bit set high:
registerWrite(bitToSet, HIGH);
}
}
// This method sends bits to the shift register:
void registerWrite(int whichPin, int whichState) {
// the bits you want to send
byte bitsToSend = 0;
// turn off the output so the pins don't light up
// while you're shifting bits:
digitalWrite(latchPin, LOW);
// turn on the next highest bit in bitsToSend:
bitWrite(bitsToSend, whichPin, whichState);
// shift the bits out:
shiftOut(dataPin, clockPin, MSBFIRST, bitsToSend);
// turn on the output so the LEDs can light up:
digitalWrite(latchPin, HIGH);
}