ultrasonic.ino

#define TRIG 13
#define ECHO 12

void setup() {
  Serial.begin (9600);
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
}

void loop() {
  long duration, distance;
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);
  duration = pulseIn(ECHO, HIGH);
  distance = (duration/2) / 29.1;

  if (distance >= 400 || distance <= 0){
    Serial.println("Out of range");
  }
  else {
    Serial.print(distance);
    Serial.println(" cm");
  }
  delay(500);
}