/*
Ultrasonic rangefinder 
********************************************
*/
#define PinTrig 12 //D6
#define PinEcho 13 //D7
long duration, distance;

void setup() {
  Serial.begin(115200);
  pinMode(PinTrig, OUTPUT);
  pinMode(PinEcho, INPUT);
  pinMode(BUILTIN_LED, OUTPUT);  
}

void loop() {
  
  digitalWrite(PinTrig, LOW);  
  delayMicroseconds(2); 
  
  digitalWrite(PinTrig, HIGH);
  delayMicroseconds(10); 
  
  digitalWrite(PinTrig, LOW);
  duration = pulseIn(PinEcho, HIGH);
  //distance round trip(cm) = time(µs) * sonic speed(cm/µs) ...
  //..distance one way = distance round trip / 2:  
  distance = duration * 0.03432 / 2;
  
  Serial.print(distance);
  Serial.print(" cm  ");
  Serial.print(duration);
  Serial.println(" µs");
  delay(200);
}