/*
 Shift Register Example
 for two 74HC595 shift registers

 This sketch turns on each of the LEDs attached to two 74HC595 shift registers,
 in sequence from output 0 to output 15.

 Hardware:
 * 2 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
 Modified 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;

char inputString[2];

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() {
 // iterate over the 16 outputs of the two shift registers
 for (int thisLed = 0; thisLed < 16; thisLed++) {
 // write data to the shift registers:
 registerWrite(thisLed, HIGH);
 // if this is not the first LED, turn off the previous LED:
 /*if (thisLed > 0) {
 registerWrite(thisLed - 1, LOW);
 } 
 // if this is the first LED, turn off the highest LED:
 else {
 registerWrite(15, LOW);
 } */
 // pause between LEDs:
 delay(1);
 }

}

// This method sends bits to the shift registers:

void registerWrite(int whichPin, int whichState) {
 // the bits you want to send. Use an unsigned int,
 // so you can use all 16 bits:
 unsigned int 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);
 Serial.println("bitWrite");
 Serial.print("bitsToSend = ");
 Serial.println(bitsToSend);
 Serial.println();

 // break the bits into two bytes, one for 
 // the first register and one for the second:
 byte registerOne = highByte(bitsToSend);
 byte registerTwo = lowByte(bitsToSend);
 Serial.print("registerOne = ");
 Serial.println(registerOne);
 Serial.println();
 Serial.print("registerTwo = ");
 Serial.println(registerTwo);
 Serial.println();

 // shift the bytes out:
 shiftOut(dataPin, clockPin, MSBFIRST, registerTwo);
 shiftOut(dataPin, clockPin, MSBFIRST, registerOne);

 // turn on the output so the LEDs can light up:
 digitalWrite(latchPin, HIGH);
}