const int echoPin = 2;
const int triggPin = 3;
long duration ;
int distance;

void setup() {
  // put your setup code here, to run once:
  pinMode(echoPin,INPUT);
  pinMode(triggPin,OUTPUT);
  Serial.begin(9600);
  Serial.println("ultrasonic sensor HC-SR04 test ");
  Serial.println("with ardiuino uno R3");

}

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(triggPin, LOW);
  delayMicroseconds(2);
  digitalWrite(triggPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggPin, LOW);

  duration = pulseIn(echoPin,HIGH);
  
  if (duration==0){
    Serial.println("no echo from sensor");

  }else{
    distance = duration*0.034/2;
    Serial.print("distance");
    Serial.print("CM");
    Serial.println(distance);
  }

}