// trig & echo pins
const int trigger = 2;
int echo = 3;

void setup() 
{
  pinMode(trigger, OUTPUT);
  pinMode(echo, INPUT);

  Serial.begin(115200);
}

void loop() 
{
  // trigger for 10 microseconds
  digitalWrite(trigger, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigger, LOW);

  // pulseIn -> measure duration (microseconds) of HIGH pulse from Echo pin
  int time = pulseIn(echo, HIGH);

  // calculate the distance in cm
  int distance = (time * 0.03432) / 2;
  delay(1000);

  Serial.print("Distance in cm: ");
  Serial.println(distance);
}