int segPins[7] = {23, 22, 21, 19, 18, 5, 17};
int digPins[4] = {2, 15, 13, 12};

byte nums[10][7] = {
  {1,1,1,1,1,1,0},
  {0,1,1,0,0,0,0},
  {1,1,0,1,1,0,1},
  {1,1,1,1,0,0,1},
  {0,1,1,0,0,1,1},
  {1,0,1,1,0,1,1},
  {1,0,1,1,1,1,1},
  {1,1,1,0,0,0,0},
  {1,1,1,1,1,1,1},
  {1,1,1,1,0,1,1}
};

int contador = 0;
int dig = 0;

unsigned long tempo = 0;

void setup() {

  for(int i=0;i<7;i++) pinMode(segPins[i], OUTPUT);
  for(int i=0;i<4;i++) pinMode(digPins[i], OUTPUT);

  for(int i=0;i<4;i++) digitalWrite(digPins[i], HIGH);
}

void setSegments(int n) {
  for(int i=0;i<7;i++) {
    digitalWrite(segPins[i], nums[n][i]);
  }
}

void allDigitsOff() {
  for(int i=0;i<4;i++) digitalWrite(digPins[i], HIGH);
}

void loop() {

  int d0 = contador / 1000;
  int d1 = (contador / 100) % 10;
  int d2 = (contador / 10) % 10;
  int d3 = contador % 10;

  allDigitsOff();

  int value;

  switch(dig) {
    case 0: value = d0; break;
    case 1: value = d1; break;
    case 2: value = d2; break;
    case 3: value = d3; break;
  }

  setSegments(value);

  digitalWrite(digPins[dig], LOW);

  delayMicroseconds(1500);

  digitalWrite(digPins[dig], HIGH);

  dig++;
  if(dig > 3) dig = 0;

  if(millis() - tempo >= 250) {
    tempo = millis();
    contador++;

    if(contador > 9999) contador = 0;
  }
}