#include "LiquidCrystal_I2C.h"

#define I2C_ADDR    0x27
#define LCD_COLUMNS 20
#define LCD_LINES   4

LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);

int temperature = 20;

void setup() {
    lcd.init();
    lcd.backlight();

    lcd.setCursor(0, 0);
    lcd.print("  I2C Protocol Demo ");
    lcd.setCursor(0, 1);
    lcd.print("====================");
    lcd.setCursor(0, 2);
    lcd.print("Slave Addr:  0x27   ");
    lcd.setCursor(0, 3);
    lcd.print("Status:  Connected! ");
    delay(3000);
}

void loop() {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("  I2C TEMPERATURE   ");
    lcd.setCursor(0, 1);
    lcd.print("====================");
    lcd.setCursor(0, 2);
    lcd.print("Temp: ");
    lcd.print(temperature);
    lcd.print(" C");
    lcd.setCursor(0, 3);
    lcd.print("Master -> Slave OK! ");
    temperature++;
    if (temperature > 40) temperature = 20;
    delay(1000);
}