int trigPin = 2;
int echoPin = 3;
void setup() 
{
  Serial.begin (9600);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() 
{
  long duration, distance;      // 시간, 거리      
  digitalWrite(trigPin, LOW);        
  delayMicroseconds(2);              
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);      // trigPin을 10마이크로초 동안 HIGH          
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration/2) / 29.1;
  Serial.print("distance = ");
  Serial.println(distance);

}