// Room Temperature Measurement with Alarm and Display on I2C LCD (NTC Thermistor Version)
// Updated with accurate NTC thermistor formula, alarm system, and button toggle using switch-case (Tinkercad compatible)

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

#define TEMP_SENSOR_PIN A1  // Analog pin for NTC thermistor
#define LED_PIN 12          // LED pin
#define BUZZER_PIN 4        // Buzzer pin
#define BUTTON_PIN 6        // Push button pin
#define TEMP_THRESHOLD 35.0 // Temperature threshold in Celsius
#define BETA 3950           // Beta coefficient of the thermistor

LiquidCrystal_I2C lcd(0x27, 16, 2); // I2C LCD initialization (address 0x27, 16x2)

bool buzzerEnabled = true; // State of buzzer (enabled by default)
int buttonState = HIGH;    // Last button state
int lastButtonState = HIGH; 
unsigned long lastDebounceTime = 0; 
unsigned long debounceDelay = 50; // Debounce time to avoid false triggers

float readTemperature() {
  int analogValue = analogRead(TEMP_SENSOR_PIN); // Read raw analog value
  float celsius = 1 / (log(1 / (1023.0 / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;
  return celsius;
}

void setup() {
  lcd.init();            // Initialize LCD
  lcd.backlight();       // Turn on LCD backlight
  
  pinMode(LED_PIN, OUTPUT);      
  pinMode(BUZZER_PIN, OUTPUT);   
  pinMode(BUTTON_PIN, INPUT_PULLUP); // Button with internal pull-up resistor

  digitalWrite(LED_PIN, LOW);    
  digitalWrite(BUZZER_PIN, LOW); 

  lcd.setCursor(0, 0);
  lcd.print("Temp: ");
  lcd.setCursor(0, 1);
  lcd.print("Buzzer: ON  ");
}

void handleButtonPress() {
  int reading = digitalRead(BUTTON_PIN);

  if (reading != lastButtonState) {
    lastDebounceTime = millis();
  }

  if ((millis() - lastDebounceTime) > debounceDelay) {
    if (reading != buttonState) {
      buttonState = reading;
      if (buttonState == LOW) { // Button pressed
        buzzerEnabled = !buzzerEnabled; // Toggle buzzer state
        lcd.setCursor(0, 1);
        if (buzzerEnabled) {
          lcd.print("Buzzer: ON   ");
          delay(1000);
        } else {
          lcd.print("Buzzer: OFF  ");
          delay(1000);
        }
      }
    }
  }

  lastButtonState = reading;
}

void loop() {
  float temperature = readTemperature();

  // Display temperature on LCD
  lcd.setCursor(6, 0);
  lcd.print(temperature, 1); // Display with one decimal place
  lcd.print((char)223);      // Degree symbol
  lcd.print("C ");

  handleButtonPress(); // Check button state and handle toggling

  switch (buzzerEnabled) {
    case true:
      if (temperature >= TEMP_THRESHOLD) {
        lcd.setCursor(0, 1);
        lcd.print("WARNING: HOT! ");
        digitalWrite(LED_PIN, HIGH); 
        digitalWrite(BUZZER_PIN, HIGH); 
      } else {
        lcd.setCursor(0, 1);
        lcd.print("Status: Normal");
        digitalWrite(LED_PIN, LOW);  
        digitalWrite(BUZZER_PIN, LOW); 
      }
      break;

    case false:
      digitalWrite(LED_PIN, LOW);  
      digitalWrite(BUZZER_PIN, LOW); 
      lcd.setCursor(0, 1);
      lcd.print("Buzzer: OFF   "); // Ensure display shows "Buzzer: OFF" when buzzer is disabled
      break;
  }

  delay(200); // Refresh rate for smoother readings
}