#define trigPin 2 // attach pin D2 Arduino to pin Echo of HC-SR04
#define echoPin 3 // attach pin D3 Arduino to pin Trig of HC-SR04  

long duration;
int distance;

void setup() {
    pinMode(trigPin, OUTPUT); //Sets the trigPin as an OUTPUT
    pinMode(echoPin, INPUT); // Sets the echoPin as an INPUT
    
    // Serial Communication is starting with 9600 of
    // baudrate speed
    Serial.begin(9600);
    // The text to be printed in serial monitor
    Serial.println("Distance measurement using ESP32.");
    delay(500);
}

void loop() {
    // Send a 10µs pulse to trigger the sensor
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);// wait for 2 ms to avoid
                         // collision in serial monitor
    digitalWrite(trigPin, HIGH);// turn on the Trigger to generate pulse
    delayMicroseconds(10);// keep the trigger "ON" for 10 ms to generate
                           // pulse for 10 ms.
    digitalWrite(trigPin, LOW);// Turn off the pulse trigger to stop
                               // pulse generation
    // Measure the time of the echo pulse
    duration = pulseIn(echoPin, HIGH);

    // Convert duration to distance (in cm)
    distance = duration * 0.0344 / 2; // Expression to calculate
                                      // distance using time
    // Display the distance
    Serial.print("Distance: ");
    Serial.print(distance);
    Serial.println(" cm");
    
    delay(5000); //the process repeats every 5 seconds.
}