/*
 Ultrasonic
*/
#define echoPin 8 // Echo Pin
#define trigPin 9 // Trigger Pin

long duration, distance; // Duration used to calculate distance

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

void loop() {

 /* The following trigPin/echoPin cycle is used to determine the
  distance of the nearest object by bouncing soundwaves off of it. */

 digitalWrite(trigPin, LOW);
 delayMicroseconds(2);

 digitalWrite(trigPin, HIGH);
 delayMicroseconds(10);

 digitalWrite(trigPin, LOW);
 duration = pulseIn(echoPin, HIGH);

 // Calculate the distance (in cm) based on the speed of sound
 // The speed of sound is 340 m/s or 29 microseconds per centimeter
 // V(m/s)＝331+0.6T(℃)
 distance = duration ;                  
 Serial.print(distance);
 Serial.println("cm");

 //Delay 50ms before next reading
 delay(50);
}