// -------------------------------------------------------------------------- //

// Define pins for the ultrasonic sensor.
const int echoPin = 25;
const int trigPin = 26;

float readSensorData();

// -------------------------------------------------------------------------- //

void setup() {
  // Begin serial communication at 115200 baud rate.
  Serial.begin(115200);

  // Set echoPin as input and trigPin as output.
  pinMode(echoPin, INPUT);
  pinMode(trigPin, OUTPUT);

  // Print sensor information to the serial monitor.
  Serial.println("Ultrasonic sensor: ");
}

// -------------------------------------------------------------------------- //

void loop() {
  // Read distance from the ultrasonic sensor.
  float distance = readSensorData();

  // Print the measured distance to the serial monitor.
  Serial.print(distance);
  Serial.println(" cm");

  // Delay between readings.
  delay(200);
}

// -------------------------------------------------------------------------- //

// Function to read data from the ultrasonic sensor.
float readSensorData() {
  // Trigger a low signal before sending a high signal.
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);

  // Send a 10-microsecond high signal to the trigPin.
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);

  // Return to low signal.
  digitalWrite(trigPin, LOW);

  // Measure the duration of the high signal on the echoPin.
  unsigned long microsecond = pulseIn(echoPin, HIGH);

  // Calculate the distance using the speed of sound (29.00µs per centimeter).
  float distance = microsecond / 29.00 / 2;

  // Return the calculated distance.
  return distance;
}

// -------------------------------------------------------------------------- //