HC-SR04 Ultrasonic sensor

Basic code

 
// defines pins numbers
const int trigPin = 2;
const int echoPin = 3;
// defines variables
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.begin(9600); // Starts the serial communication
}
void loop() {
  // Clears the trigPin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin on HIGH state for 10 micro seconds
  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 = duration * 0.034 / 2;
  // Prints the distance on the Serial Monitor
  Serial.print("Distance: ");
  Serial.println(distance);
}

Noise reduction code

 
// Constants
const int WINDOW_SIZE = 10; // Adjust the window size as needed
const int sensorTriggerPin = 2; // Connect to the trigger pin of HC-SR04
const int sensorEchoPin = 3; // Connect to the echo pin of HC-SR04
const int glitchThreshold = 2000; // Threshold for excluding glitchy readings

// Variables
int readings[WINDOW_SIZE]; // Array to store recent sensor readings
int index = 0; // Index for circular buffer
long sum = 0; // Sum of recent readings

void setup() {
    Serial.begin(9600);
    pinMode(sensorTriggerPin, OUTPUT);
    pinMode(sensorEchoPin, INPUT);
}

void loop() {
    // Trigger the sensor
    digitalWrite(sensorTriggerPin, LOW);
    delayMicroseconds(2);
    digitalWrite(sensorTriggerPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(sensorTriggerPin, LOW);

    // Read the echo pulse duration
    long duration = pulseIn(sensorEchoPin, HIGH);

    // Calculate distance in centimeters
    float distance_cm = duration * 0.034 / 2;

    // Exclude glitchy readings
    if (distance_cm < glitchThreshold) {
        // Add the new reading to the window
        sum -= readings[index]; // Subtract the oldest reading
        readings[index] = distance_cm; // Store the new reading
        sum += distance_cm; // Add the new reading

        // Increment the index (circular buffer)
        index = (index + 1) % WINDOW_SIZE;

        // Calculate the moving average
        float movingAverage = static_cast<float>(sum) / WINDOW_SIZE;

        // Convert movingAverage to an integer
        int filteredDistance = static_cast<int>(movingAverage);

        // Print the filtered distance (as an integer)
        Serial.print("Filtered Distance: ");
        Serial.println(filteredDistance);

        // Add any additional logic or actions based on the filtered value
        // (e.g., control a motor, trigger an alarm, etc.)
    }

    // Add any other necessary logic here

    delay(100); // Adjust the delay as needed
}