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//**************************************************************// // Name : shiftOutCode, Dual Binary Counters // // 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() {

  //Start Serial for debuging purposes	
  Serial.begin(9600);
  //set pins to output because they are addressed in the main loop
  pinMode(latchPin, 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, 0);
    //count up on GREEN LEDs
    shiftOut(dataPin, clockPin, j); 
    //count down on RED LEDs
    shiftOut(dataPin, clockPin, 255-j);
    //return the latch pin high to signal chip that it 
    //no longer needs to listen for information
    digitalWrite(latchPin, 1);
    delay(1000);
  }

}

void shiftOut(int myDataPin, int myClockPin, byte myDataOut) {

  // This shifts 8 bits out MSB first, 
  //on the rising edge of the clock,
  //clock idles low

..//internal function setup

  int i=0;
  int pinState;
  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, OUTPUT);

. //clear everything out just in case to . //prepare shift register for bit shifting

  digitalWrite(myDataPin, 0);
  digitalWrite(myClockPin, 0);

  //for each bit in the byte myDataOut…
  //NOTICE THAT WE ARE COUNTING DOWN in our for loop
  //This means that %00000001 or "1" will go through such
  //that it will be pin Q0 that lights. 
  for (i=7; i>=0; i--)  {
    digitalWrite(myClockPin, 0);

    //if the value passed to myDataOut and a bitmask result 
    // true then... so if we are at i=6 and our value is
    // %11010100 it would the code compares it to %01000000 
    // and proceeds to set pinState to 1.
    if ( myDataOut & (1<<i) ) {
      pinState= 1;
    }
    else {	
      pinState= 0;
    }

    //Sets the pin to HIGH or LOW depending on pinState
    digitalWrite(myDataPin, pinState);
    //register shifts bits on upstroke of clock pin  
    digitalWrite(myClockPin, 1);
    //zero the data pin after shift to prevent bleed through
    digitalWrite(myDataPin, 0);
  }

  //stop shifting
  digitalWrite(myClockPin, 0);

}