const int DS = 8;
const int STCP = 9;
const int SHCP = 10;

void writeBinaryNumber(int n) {
  if (n >= 0 and n <= 255) {
    digitalWrite(STCP, LOW);
    shiftOut(DS, SHCP, MSBFIRST, n);
    digitalWrite(STCP, HIGH);
  }
}

void setup() {
  pinMode(DS, OUTPUT);
  pinMode(STCP, OUTPUT);
  pinMode(SHCP, OUTPUT);
  writeBinaryNumber(0);
  Serial.begin(115200);
  Serial.println("Escriba un número entre 0 y 255:");
}

void loop() {
  if(Serial.available()) {
    String data = Serial.readStringUntil('\n');
    writeBinaryNumber(data.toInt());
  }
}