#define TRIG 9
#define ECHO 10
long duration;
float distance;

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

void loop() {
  digitalWrite(TRIG , LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG , HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG , LOW);
  duration = pulseIn(ECHO , HIGH);
  distance = duration * 0.034/2;
  Serial.print("Distance : ");
  Serial.print(distance);
  Serial.println("cm");
  delay(500);
}