Complete Guide for Ultrasonic Sensor HC-SR04

/*
 * created by Rui Santos, http://randomnerdtutorials.com
 * 
 * Complete Guide for Ultrasonic Sensor HC-SR04
 *
    Ultrasonic sensor Pins:
        VCC: +5VDC
        Trig : Trigger (INPUT) - Pin11
        Echo: Echo (OUTPUT) - Pin 12
        GND: GND
 */

int trigPin = 11;    //Trig - green Jumper
int echoPin = 12;    //Echo - yellow Jumper
int duration;
int cm;
int inches;

void setup() {
  //Serial Port begin
  Serial.begin (9600);
  //Define inputs and outputs
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}

void loop() {

  digitalWrite(trigPin, HIGH);
  delayMicroseconds(50);
  digitalWrite(trigPin, LOW);
  delayMicroseconds(10);
  duration = pulseIn(echoPin, HIGH);
 
  // convert the time into a distance
  cm = (duration/2) / 29.1;
  inches = (duration/2) / 74; 
  
  //prints distance in "cm" and "inches"
  Serial.print(cm);
  Serial.print(" cm    ,");
  Serial.print(inches);
  Serial.println(" in");
  delayMicroseconds(300);
}