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

#define LCD_COLUMNS 20
#define LCD_LINES   4

#define RTC 0x68   // I2C 7-bit address
#define LCD 0x27   // I2C 7-bit address

LiquidCrystal_I2C lcd(LCD, LCD_COLUMNS, LCD_LINES);

void setup() {
  Wire.begin();
  lcd.init();
}

void loop() {
  uint8_t mm, ss;
  Wire.beginTransmission(RTC);
  Wire.write(0x00);
  Wire.endTransmission(false);
  Wire.requestFrom(RTC, 2);
    
  ss = Wire.read() & 0x7F;
  mm = Wire.read() & 0x7F;
  lcd.setCursor(0, 1);
  lcd.print(mm >> 4);
  lcd.print(mm & 0x0F);
  lcd.print(":");
  lcd.print(ss >> 4);
  lcd.print(ss & 0x0F);
}