#include <Wire.h>

#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd (0X27, 24, 2);

byte hours = 15, minutes = 17, seconds = 5;
byte days = 3, months = 5, years = 19;

byte bcdToDec(byte val){
  val = val / 16 * 10 + val % 16;
  return val;
}

byte decToBcd(byte val){
  val = val / 10 * 16 + val % 10;
  return val;
}

void setupTime(int second, int minute, int hour){
  Wire.beginTransmission(0x68);
  Wire.write(0x0);
  Wire.write(decToBcd(second));
  Wire.write(decToBcd(minute));
  Wire.write(decToBcd(hour));
  Wire.endTransmission();
}

void readTime(){
  Wire.beginTransmission(0x68);
  Wire.write(0x0);
  Wire.endTransmission();
  Wire.requestFrom(0x68, 3);
  if(Wire.available()){
    seconds = bcdToDec(Wire.read());
    minutes = bcdToDec(Wire.read());
    hours = bcdToDec(Wire.read() & 0b111111);
  }
}

void printTime(){
  readTime();

  lcd.setCursor(0, 0);
  Serial.print(hours / 10);
  lcd.setCursor(1, 0);
  Serial.print(hours % 10);
  lcd.setCursor(2, 0);
  Serial.print(":");
  lcd.setCursor(3, 0);
  Serial.print(minutes / 10);
  lcd.setCursor(4, 0);
  Serial.print(minutes % 10);
}

void setupDate(int day, int month, int year) {
  Wire.beginTransmission(0x68);
  Wire.write(0x3);
  Wire.write(0);
  Wire.write(decToBcd(day));
  Wire.write(decToBcd(month));
  Wire.write(decToBcd(year));
  Wire.endTransmission();
}

void readDate(){
  Wire.beginTransmission(0x68);
  Wire.write(3);
  Wire.endTransmission();
  Wire.requestFrom(0x68,4);
  if(Wire.available()){
    bcdToDec(Wire.read());
    days = bcdToDec(Wire.read());
    months = bcdToDec(Wire.read());
    years = bcdToDec(Wire.read());
  }
}

void printDate(){
  readDate();
  lcd.setCursor(6, 0);
  Serial.print(dateArray[0] / 10);
  lcd.setCursor(7, 0);
  Serial.print(dateArray[0] % 10);
  lcd.setCursor(8, 0);
  Serial.print("/");
  lcd.setCursor(9, 0);
  Serial.print(dateArray[1] / 10);
  lcd.setCursor(10, 0);
  Serial.print(dateArray[1] % 10);
  lcd.setCursor(11, 0);
  Serial.print("/");
  lcd.setCursor(12, 0);
  Serial.print(dateArray[2] / 10);
  lcd.setCursor(13, 0);
  Serial.print(dateArray[2] % 10);
}

void setup() {
  Serial.begin(9600);

  Wire.begin();

  lcd.begin();
  lcd.backlight();

  setupTime(seconds, minutes, hours);
  setupDate(days, months, years);
}

void loop() {
  printTime();
  printDate();
}