Distance Measurement with an Ultrasonic Sensor HY-SRF05

1const unsigned int TRIG_PIN=13;
2const unsigned int ECHO_PIN=12;
3const  unsigned int BAUD_RATE=9600;
4
5void setup() {
6  pinMode(TRIG_PIN, OUTPUT);
7  pinMode(ECHO_PIN, INPUT);
8  Serial.begin(BAUD_RATE);
9}
10
11void loop()  {
12  digitalWrite(TRIG_PIN, LOW);
13  delayMicroseconds(2);
14  digitalWrite(TRIG_PIN,  HIGH);
15  delayMicroseconds(10);
16  digitalWrite(TRIG_PIN, LOW);
17  
18
19  const unsigned long duration= pulseIn(ECHO_PIN, HIGH);
20 int distance= duration/29/2;
21  if(duration==0){
22   Serial.println("Warning: no pulse from sensor");
23   }  
24  else{
25      Serial.print("distance to nearest object:");
26      Serial.println(distance);
27      Serial.println(" cm");
28  }
29 delay(100);
30 }