#include <Wire.h>

const int buttonPin = 26;
const int ledPin = 27;
const int tempSensorPin = 35;  

// Parameters for the Voltage Divider
const float Vref = 3.3;      // ESP32 ADC reference voltage
const int ADC_Max = 4095;    // 12-bit ADC resolution
const int R_fixed = 10000;   // Fixed resistor value (10kΩ)

bool buttonState = false;    // Variable to hold the button state

void setup() {
  // Initialize serial communication
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);        // Set LED pin as output
  pinMode(buttonPin, INPUT_PULLUP); // Set button pin as input with internal pull-up resistor
}

void loop() {
  bool currentButtonState = digitalRead(buttonPin) == HIGH; // Button pressed when HIGH

  if (currentButtonState != buttonState) {
    if (currentButtonState) {
      digitalWrite(ledPin, HIGH); // Turn LED on
      Serial.println("Button pressed");
    } else {
      digitalWrite(ledPin, LOW);  // Turn LED off
      Serial.println("Button released");
    }
    buttonState = currentButtonState; // Update button state
  }

  // Read temperature sensor value (analog voltage) from the temperature sensor and store it in tempValue
  int tempValue = analogRead(tempSensorPin); 

  // Avoid division by zero by checking if Vout is close to Vref
  if (tempValue == 0 || tempValue == ADC_Max) { // If tempValue is 0 or equals ADC_Max (typically 1023 for a 10-bit ADC)
    Serial.println("Invalid sensor reading."); //  If an invalid reading is detected, it prints "Invalid sensor reading"
  } else {
    // Convert analog value to voltage
    float Vout = tempValue * (Vref / ADC_Max); //Vout is computed by scaling tempValue to the reference voltage (Vref)

    // 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 Beta = 3950.0;     // Beta parameter for the NTC thermistor
    float T0 = 298.15;       // Reference temperature (25°C in Kelvin)
    float R0 = 10000.0;      // NTC resistance at 25°C (10kΩ)
    float temperatureK = (Beta * T0) / (Beta + (T0 * log(R_NTC / R0))); // Beta Parameter eauatioq
    float temperatureC = temperatureK - 273.15; Converting to Celsius

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

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