int dataPin = 18;
int latchPin = 20;
int clockPin = 21;
int comPin[] = { 14, 15, 16, 17 }; // Common pins

// Define the characters 0-F (1 segment off 0 on)
byte num[] = {
  0b11000000, // 0
  0b11111001, // 1
  0b10100100, // 2
  0b10110000, // 3
  0b10011001, // 4
  0b10010010, // 5
  0b10000010, // 6
  0b11111000, // 7
  0b10000000, // 8
  0b10010000, // 9
  0b10001000, // A
  0b10000011, // B
  0b10100111, // C
  0b10100001, // D
  0b10000110, // E
  0b10001110, // F
};

void setup()
{ // set pins to output

  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  for (int i = 0; i < 4; i++) {
    pinMode(comPin[i], OUTPUT);
    digitalWrite(comPin[i], HIGH);
  }
}

void loop()
{
  writeData(0xff);
  selectDigitalDisplay(0);
  for (int i = 0; i < 16; i++) {
    writeData(num[i]);
    delay(500);
  }
  for (int x = 0; x < 100; x++) {
    for (int i = 0; i < 4; i++) {
      selectDigitalDisplay(i);
      writeData(num[i]);
      delay(5);
      writeData(0xff);
    }
    delay(5);
  }
}


void selectDigitalDisplay(byte com)
{
  for (int i = 0; i < 4; i++) {
    digitalWrite(comPin[i], LOW);
  }
  digitalWrite(comPin[com], HIGH);
}

void writeData(int value)
{
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, value);
  digitalWrite(latchPin, HIGH);
}