#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

uint8_t ndx = 0;
uint8_t ndx2 = 0;
uint8_t num = 0;

void updateShiftRegister()
{
  digitalWrite(LATCH_PIN, LOW);
  shiftOut(DATA_PIN, CLOCK_PIN, MSBFIRST, num);
  digitalWrite(LATCH_PIN, HIGH);
}

void increment () {
  ndx2 = random(0, 8);
  //Serial.print("ndx2 = ");
  Serial.println(ndx2);
  if (ndx2 == ndx) return;
  if (ndx2 > ndx ) {

    for (uint8_t i = ndx; i <= ndx2; i++) {
      bitSet(num, ndx);
      updateShiftRegister();
      //Serial.print(num);
      //Serial.print(" ");
      if (i < ndx2) {
        ndx ++;
      }
      delay(20);
    }
    //Serial.println();
    //Serial.println(ndx);
  }
  else {  
    for (uint8_t i = ndx; i >= ndx2; i--) {
      bitClear(num, ndx);
      updateShiftRegister();
      //Serial.print(num);
      //Serial.print(" ");
      if (ndx == 0) break;
      if (ndx > ndx2) {  
        ndx --;
      }
      delay(20);
    }
    //Serial.println();
    //Serial.println(ndx);  
  }


}

void setup() {
  // put your setup code here, to run once:
  pinMode(DATA_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
  pinMode(LATCH_PIN, OUTPUT);
  Serial.begin(115200);
  Serial.println("Hello World");

}

void loop() {
  // put your main code here, to run repeatedly:
  increment();
  delay(100);


}