/*
   Arduino code for Individual control over each pin
   Support for 40+ 74HC595 8 bit shift registers
   http://bildr.org/2011/02/74hc595/
*/

#define DATA_PIN  8  // Pin connected to DS of 74HC595
#define LATCH_PIN 9  // Pin connected to STCP of 74HC595
#define CLOCK_PIN 10 // Pin connected to SHCP of 74HC595

// How many of the shift registers
#define NUM_SHIFT_REGS 3

// definenumber of output pins 
// each shift register has 8 output pins, 3 input pins
const uint8_t numOfRegisterPins = NUM_SHIFT_REGS * 8;

// array of registers
bool registers[numOfRegisterPins];

void setup() {
  pinMode(DATA_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
  pinMode(LATCH_PIN, OUTPUT);
  clearRegisters();
  writeRegisters();
}

void loop() {
  oneAfterAnother();
  clearRegisters();
}

// to clear registers of previous outputs
void clearRegisters() {
  // Reset all register pins
  for (int i = numOfRegisterPins - 1; i >= 0; i--) {
    registers[i] = HIGH; 
    // high because rgb led are not grounded but are provided 5v
  }
}

void setRegisterPin(int index, int value) {
  // Set an individual pin HIGH or LOW
  registers[index] = value;
}

void oneAfterAnother()
{
// This function will turn on all the LEDs, one-by-one,
// and then turn them off all off, one-by-one. 

  int index;
  int delayTime = 100; // Time (milliseconds) to pause between LEDs
  // Make this smaller for faster switching

  for(index = 23; index >= 16; index--)
  {
    // LOW because we want that pin to act as ground
    setRegisterPin(index,LOW);
    writeRegisters();
    delay(delayTime);
  }

  clearRegisters();

  for(index = 15; index >= 8; index--)
  {
    setRegisterPin(index,LOW);
    writeRegisters();
    delay(delayTime);
  }

  clearRegisters();

  for(index = 7; index >= 0; index--)
  {
    setRegisterPin(index,LOW);
    writeRegisters();
    delay(delayTime);
  }

  // Turn all the LEDs off
  
}

// write on registers
void writeRegisters() {
  // Set and display registers
  digitalWrite(LATCH_PIN, LOW);

  for (int i = numOfRegisterPins - 1; i >= 0; i--) {
    digitalWrite(CLOCK_PIN, LOW);
    digitalWrite(DATA_PIN, registers[i]);
    digitalWrite(CLOCK_PIN, HIGH);
  }

  digitalWrite(LATCH_PIN, HIGH);
}