const int echoPin = 3;
const int trigPin = 2;
 
void setup() {
  Serial.begin(9600);                   
  pinMode(echoPin, INPUT);               
  pinMode(trigPin, OUTPUT);              
  Serial.println("Ultrasonic sensor:");
}
 
void loop() {
  float distance = readDistance();      
  
  if (distance > 400) {             
    Serial.println("Out of Range");      
  } else {
    Serial.print(distance);              
    Serial.println(" cm");               
  }
  
  delay(400);                            
}
 

float readDistance() {
  digitalWrite(trigPin, LOW);        
  delayMicroseconds(2);                  
  digitalWrite(trigPin, HIGH);         
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);           
 

  float pulse_duration = pulseIn(echoPin, HIGH); 
  float distance = pulse_duration / 58.00;      
  
  return distance;                               
}