#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 4

// 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() {
  // put your setup code here, to run once:
  pinMode(DATA_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
  pinMode(LATCH_PIN, OUTPUT);
  clearRegisters();
}


int anodePins[] = {24,25,26,27,28,29,30,31};

void loop() {
  // put your main code here, to run repeatedly:
  clearRegisters();
  chaseRed();
}


void chaseRed(){
  clearRegisters();
  // setRegisterPin(0,LOW);
  for(int i=2; i<8; i++){
    setRegisterPin(i,HIGH);
    writeRegisters();
    delay(100); 
  }
  for(int i=0; i<8; i++){
    setRegisterPin(i,HIGH);
    writeRegisters();
    delay(100); 
  }
}

// to clear registers of previous outputs
void clearRegisters() {
  // Reset all register pins
  for (int i = numOfRegisterPins - 1; i >= 0; i--) {
    registers[i] = LOW; 
    // 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;
}

// 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);
}