Recebendo comandos via porta serial no Arduino Mega

recebe_serial.c

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);
  while (!Serial);
  // send an intro:
  Serial.println("\nSerial INPUT!");
}

void loop() {
  // Read serial input:
  while (Serial.available() > 0) {
    int input = Serial.read();
    Serial.println(input);
    Serial.println((char)input);
    if (isDigit(input)) {
      int number = (int)(input - 48);
      blink_led(number);
    }
  }
}

void blink_led(int led) {
  digitalWrite(led, HIGH);
  delay(1000); 
  digitalWrite(led, LOW);
}