#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

const float BETA = 3950; // Beta Coefficient of the thermistor

// OLED display I2C address (usually 0x3C or 0x3D)
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET    -1

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

void setup() {
  Serial.begin(9600);
  
  // Initialize the display
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3D)) {
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);  // Infinite loop if display initialization fails
  }
  
  // Clear the display
  display.clearDisplay();
  display.setTextSize(1);      // Normal 1:1 pixel scale
  display.setTextColor(SSD1306_WHITE); // Draw white text
  display.setCursor(0,0);      // Start at top-left corner
  
  pinMode(3, OUTPUT); // Green LED
  pinMode(5, OUTPUT); // Red LED
}

void loop() {
  int analogValue = analogRead(A0);
  
  // Avoid division by zero
  if (analogValue > 0) {
    float celsius = 1 / (log(1 / (1023.0 / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;

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

    // Clear the display and print the temperature
    display.clearDisplay();
    display.setCursor(0, 0);
    display.print("Temperature: ");
    display.print(celsius, 1); // Display temperature with 1 decimal place
    display.print(" C");
    display.display();

    // Check if temperature is in the range 20 to 25
    if (celsius > 20 && celsius < 25) {
      digitalWrite(3, HIGH); // Turn green LED on
      delay(100);
      digitalWrite(3, LOW); // Turn green LED off
      delay(100);
      digitalWrite(5, LOW); // Turn red LED off
    } else {
      digitalWrite(5, HIGH); // Turn red LED on
      delay(100);  
      digitalWrite(5, LOW); // Turn red LED off
      delay(100);  
      digitalWrite(3, LOW); // Turn green LED off
    }
  } else {
    Serial.println("Invalid analog value.");
  }

  delay(100); // Wait 1 second before repeating
}