Arduino Watch Frog (HC-SR04 door distance alarm)

arduino-watch-frog-sketch

// ---------------------------------------------------------------- //
// Arduino Watch Frog (HC-SR04 door distance alarm)
// Place with sensor facing a closed door and then attach power. 
// Alarm will sound if distance to door changes in either direction
// beyond the THRESHOLD. Alarm will not stop until power is disconnected.
// Tested on 10 September 2020
// Author: Dan Nicholson (github.com/danic85)
// ---------------------------------------------------------------- //

#define echoPin 7 // Echo of HC-SR04
#define trigPin 6 // Trig of HC-SR04
#define buzzerPin 4 // Buzzer output
#define ledPin 13 // LED output
#define THRESHOLD 5 // Distance change before sounding alarm (cm)

long duration; // Duration of sound wave travel
int distance; // Distance measurement
int startingDistance; // Initial measurement

void setup() {
  pinMode(trigPin, OUTPUT); // Sets the trigPin as an OUTPUT
  pinMode(echoPin, INPUT); // Sets the echoPin as an INPUT
  pinMode(buzzerPin, OUTPUT); // Sets the buzzerPin as an OUTPUT
  pinMode(ledPin, OUTPUT); // Sets the ledPin as an OUTPUT
  startingDistance = getDistance();
}
void loop() {
    delay(500);
    if (getDistance() < startingDistance - THRESHOLD || getDistance() > startingDistance + THRESHOLD)
    {
      // Do this forever!
      while (true) {
        buzz(HIGH);
        delay(500);
        buzz(LOW);
        delay(500);
      }
    }
}

int getDistance() {
  // Clears the trigPin condition
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  // Sets the trigPin HIGH (ACTIVE) for 10 microseconds
  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; // Speed of sound wave divided by 2 (go and back)
  return distance;
}

void buzz(int val) {
  digitalWrite(buzzerPin,val);
  digitalWrite(ledPin,val);
}