const int triggerPin = 6;     //we'll set up a global variable for our trigger pin as pin 6
const int echoPin = 7;        //we'll set up a global variable for echo pin as pin 7

void setup() {
  pinMode(triggerPin, OUTPUT);  //We need to set up our arduino's trigger pin as an OUTPUT
  pinMode(echoPin, INPUT);      //We also need to set up the arduino pin connected to echo as an INPUT
  Serial.begin(9600);           //We'll start the serial monitor and spit out our actual measurements there
}
void loop() {
  digitalWrite(triggerPin, HIGH); //We need to send a pulse to our trigger pin of at least 10 microseconds
  delayMicroseconds(10);
  digitalWrite(triggerPin, LOW);
  int echoTime = pulseIn(echoPin, HIGH); //We cheat and use the pulseIn instruction to simply time the HIGH pulse coming from our echo pin
  //Now let's do some maths
  float cmDistance = (echoTime / 2) * 0.0344;
  
  Serial.print("Distance: ");
  Serial.print(cmDistance);
  Serial.println(" mm,  ");
  delay(250);
}