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

// LCD I2C address and dimensions
LiquidCrystal_I2C lcd(0x27, 16, 2);

// Pin definitions
const int tempSensorPin = 33; // Analog pin connected to the voltage divider
const int buttonPin = 12;     // Digital pin connected to the button
const int ledPin = 14;        // Digital pin connected to the LED

// Constants for temperature calculation
const float Vref = 3.3;       // Reference voltage
const int ADC_Max = 4095;     // Maximum ADC value for ESP32 (12-bit ADC)
const float R_fixed = 10000;  // Fixed resistor value in ohms
const float Beta = 3950.0;    // Beta parameter for the NTC thermistor
const float T0_ref = 298.15; // Reference temperature (25°C in Kelvin)
const float R0 = 10000.0;     // NTC resistance at 25°C (10kΩ)

void setup() {
  // Initialize serial communication
  Serial.begin(115200);

  // Initialize the LCD
  lcd.init();
  lcd.backlight();

  // Initialize the button pin
  pinMode(buttonPin, INPUT_PULLUP);

  // Initialize the LED pin
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Read temperature sensor value
  int tempValue = analogRead(tempSensorPin);

  // Avoid division by zero by checking if Vout is close to Vref
  if (tempValue == 0 || tempValue == ADC_Max) {
    Serial.println("Invalid sensor reading.");
  } else {
    // Convert analog value to voltage
    float Vout = tempValue * (Vref / ADC_Max);

    // Calculate the NTC resistance using the Voltage Divider formula
    float R_NTC = (R_fixed * (Vref - Vout)) / Vout;

    // Calculate Temperature using the Beta parameter equation
    float temperatureK = (Beta * T0_ref) / (Beta + (T0_ref * log(R_NTC / R0)));
    float temperatureC = temperatureK - 273.15; // Convert to Celsius

    // Print the temperature to Serial Monitor
    Serial.print("Temperature: ");
    Serial.print(temperatureC);
    Serial.println(" °C");

    // Display appropriate message based on temperature on LCD
    lcd.clear();
    if (temperatureC < 15) {
      lcd.print("Cold");
    } else if (temperatureC >= 15 && temperatureC <= 25) {
      lcd.print("Normal");
    } else {
      lcd.print("Hot");
    }

    // Display the temperature on the second line of the LCD
    lcd.setCursor(0, 1);
    lcd.print(temperatureC);
    lcd.print(" C");
  }

  delay(1000); // Delay 1 second before next reading
}