// ---------------------------------------------------------------- //
// Using HC-SR04 Ultrasonic Sensor Module
// ---------------------------------------------------------------- //
 
constexpr uint8_t echoPin = 12  // attach pin D12 Arduino to pin Echo of HC-SR04
constexpr uint8_t trigPin = 13  //attach pin D13 Arduino to pin Trig of HC-SR04
 
// defines variables
long duration; // variable for the duration of sound wave travel
int distance_cm; // variable for centimeters measurement
int distance_inch; // variable for inches measurement
 
void setup() {
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an OUTPUT
  pinMode(echoPin, INPUT); // Sets the echoPin as an INPUT
  Serial.begin(115200); // // Serial Communication is starting with 9600 of baudrate speed
  Serial.println("Ultrasonic Sensor HC-SR04 Test"); // print some text in Serial Monitor
  Serial.println("with Arduino Mega 2560 R3");
}
void loop() {
  // Clears the trigPin condition
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin HIGH (ACTIVE) for 10 microseconds
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  // Reads the echoPin, returns the sound wave travel time in microseconds
  duration = pulseIn(echoPin, HIGH);
  // Calculating the distance
  distance_cm = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)
  distance_inch = duration * 0.0133 / 2; // Speed of sound wave divided by 2 (go and back)
  // Displays the distance on the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance_cm);
  Serial.print(" cm, ");
  Serial.print(distance_inch);
  Serial.println(" inch");
  delay(200);
}