int echo = 4; // GPIO 4 (D2) connected to the echo pin of the ultrasonic sensor
int trigger = 5; // GPIO 5 (D1) connected to the trigger pin of the ultrasonic sensor
long traveltime; // Variable to store the time duration
float distance; // Variable to store the calculated distance

void setup() {
  pinMode(trigger, OUTPUT); // Declare trigger pin as output
  pinMode(echo, INPUT); // Declare echo pin as input
  Serial.begin(9600); // Start the serial communication at 9600 baud rate
}

void loop() {
  // Trigger the ultrasonic sensor
  digitalWrite(trigger, LOW);
  delayMicroseconds(2); // Delay of 2 microseconds
  digitalWrite(trigger, HIGH);
  delayMicroseconds(10); // Send a 10-microsecond pulse
  digitalWrite(trigger, LOW);

  // Measure the time for the echo
  traveltime = pulseIn(echo, HIGH);

  // Calculate the distance
  distance = traveltime * 0.034 / 2; // Convert time to distance (cm)

  // Print the distance on the serial monitor
  Serial.print("Distance = ");
  Serial.print(distance);
  Serial.println(" cm");

  delay(100); // Wait for 100ms before the next measurement
}