#include <LCD_I2C.h>

#define TRIGGER_PIN 2  // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN    3  // Arduino pin tied to echo pin on the ultrasonic sensor.
#define BUZZER_PIN 9   // Arduino pin tied to 1 of the pins on the speaker/buzzer.
#define E5_NOTE 659.25
#define E6_NOTE 1318.51

LCD_I2C lcd(0x27, 16, 2);


double ALARM[] = {
  E5_NOTE, E6_NOTE
};



void setup() {
  pinMode(TRIGGER_PIN, OUTPUT); // Set the trigger pin as an output:
  pinMode(ECHO_PIN, INPUT);     // Set the echo pin as an input:
  lcd.begin();
  lcd.backlight();
}

void loop() {
  // Clear the trigger pin condition:
  digitalWrite(TRIGGER_PIN, LOW);
  delayMicroseconds(2);
  // Sets the trigger pin to HIGH state for 10 microseconds:
  digitalWrite(TRIGGER_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIGGER_PIN, LOW);

  // Reads the echo pin, and returns the sound wave travel time in microseconds:
  long duration = pulseIn(ECHO_PIN, HIGH);

  // Calculate the distance:
  long distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and back)

  

  //Display the distance on the LCD screen:

  lcd.setCursor(2, 0);
  lcd.print("Distance: ");
  lcd.print(distance);


  // Set an alarm to ring if the person gets closer than desired distance:

  if(distance < 25){
    tone(BUZZER_PIN, ALARM, 100000);
    lcd.setCursor(2, 1);
    lcd.print("ALARM ON!");
  }  
  else {
    noTone(BUZZER_PIN);
    lcd.clear();
  }

  
  delay(20); // Wait for 500 milliseconds before next loop for the next distance reading.
}