/* ---------------------------------------------------------------
 *  Example code for HC-SR04 ultrasonic distance sensor with Arduino. 
 *  https://www.makerguides.com/hc-sr04-arduino-tutorial/
 *  No library is required to use this sensor.
 *  Setup:
 *        HC-SR04 has 4 connections: 5v, Gnd 
 *                                   echo -> pin2
 *                                   trig -> pin3
 ----------------------------------------------------------------*/
 
// Define Trigger and Echo pin:
#define trigPin 3
#define echoPin 2

long duration;
int distance;

void setup() {
  // Define inputs and outputs:
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  //Begin Serial communication at a baudrate of 9600:
  Serial.begin(9600);
}
void loop() {
  // "Clear" the trigPin by setting it LOW:
  digitalWrite(trigPin, LOW);
  delayMicroseconds(5);
  // Generate pulse by setting the trigPin high for 10 microseconds:
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  // Read the echoPin, pulseIn() returns the duration (length of the pulse) in microseconds:
  duration = pulseIn(echoPin, HIGH);
  // Calculate the distance:
  distance = duration * 0.034 / 2;
  // Print the distance on the Serial Monitor (Ctrl+Shift+M):
  Serial.print("Distance = ");
  Serial.print(distance);
  Serial.println(" cm");
  delay(50);
}