#define TRIG_PIN 9
#define ECHO_PIN 10
#define LED_PIN 7
#define BUZZER_PIN 6

float getDistance()
{
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);

  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);

  digitalWrite(TRIG_PIN, LOW);

  long duration = pulseIn(ECHO_PIN, HIGH);

  float distance = duration * 0.034 / 2;

  return distance;
}

void setup()
{
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  pinMode(LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);

  Serial.begin(9600);
}

void loop()
{
  float total = 0;
  for(int i = 0; i < 5; i++)
  {
    total += getDistance();
    delay(20);
  }

  float distance = total / 5;

  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  if(distance < 20 && distance > 0)
  {
    digitalWrite(LED_PIN, HIGH);
    tone(BUZZER_PIN, 1000);
  }
  else
  {
    digitalWrite(LED_PIN, LOW);
    noTone(BUZZER_PIN);
  }

  delay(1000);
}