#include <LiquidCrystal_I2C.h>
#include <RTClib.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);
RTC_DS3231 rtc;

//const char* week_days[7] = {"SUN", "MON", "TUE", "WED", "THU", "FRI", "SAT"};
const String week_days[7] = {"SUN", "MON", "TUE", "WED", "THU", "FRI", "SAT"};

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

  rtc.begin();
  //rtc.adjust(DateTime(F(__DATE__),F(__TIME__)));
}

void loop() {
  DateTime now = rtc.now();
  char t[17]="";

  sprintf(t, "%04d-%02d-%02d ", now.year(), now.month(), now.day());
  lcd.setCursor(0, 0);
  lcd.print(t);
  lcd.print(week_days[now.dayOfTheWeek()]);
  /*
  lcd.print(now.year());
  lcd.print("-");
  lcd.print(now.month());
  lcd.print("-");
  lcd.print(now.day());
  lcd.print(" ");
  lcd.print(week_days[now.dayOfTheWeek()]);
  */
  sprintf(t, "%02d:%02d:%02d", now.hour(), now.minute(), now.second());
  lcd.setCursor(0, 1);
  lcd.print(t);
  /*
  lcd.print(now.hour()/10);
  lcd.print(now.hour()%10);
  lcd.print(":");
  lcd.print(now.minute()/10);
  lcd.print(now.minute()%10);
  lcd.print(":");
  lcd.print(now.second()/10);
  lcd.print(now.second()%10);
  */
  delay(1000);
}




/*
#include <LiquidCrystal_I2C.h>
#include <RTClib.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);
RTC_DS3231 rtc;

// 사용자정의 문자용 비트맵 이미지
byte char_a[8]={B11111, B11111, B11111, B11111, B11111, B11111, B11111, B11111};
byte char_b[8]={B11111, B11111, B00000, B00000, B00000, B00000, B00000, B00000};
byte char_c[8]={B00000, B00000, B00000, B00000, B00000, B00000, B11111, B11111};
byte char_d[8]={B11111, B11111, B00000, B00000, B00000, B00000, B11111, B11111};
byte char_f[8]={B00000, B00000, B00011, B00011, B00011, B00011, B00000, B00000};
byte char_g[8]={B00000, B00000, B10000, B10000, B10000, B10000, B00000, B00000};

// 큰 숫자 표시용 사용자정의 문자
int big_num[10][6]={
  {1, 2, 1, 1, 3, 1},   //0
  {2, 1, 32, 3, 1, 3},  //1
  {4, 4, 1, 1, 3, 3},   //2
  {4, 4, 1, 3, 3, 1},   //3
  {1, 3, 1, 32, 32, 1}, //4
  {1, 4, 4, 3, 3, 1},   //5
  {1, 4, 4, 1, 3, 1},   //6
  {1, 2, 1, 32, 32, 1}, //7
  {1, 4, 1, 1, 3, 1},   //8
  {1, 4, 1, 3, 3, 1}    //9
};


void setup() {
  lcd.init();
  lcd.backlight();
  lcd.clear();
  rtc.begin();

  //사용자문자 정의
  lcd.createChar(1, char_a);
  lcd.createChar(2, char_b);
  lcd.createChar(3, char_c);
  lcd.createChar(4, char_d);
  lcd.createChar(6, char_f);
  lcd.createChar(7, char_g);
}

void loop() {
  DateTime now = rtc.now();
  
  disp_num(0, now.hour()/10);
  disp_num(4, now.hour()%10);
  disp_colon(7);
  disp_num(9, now.minute()/10);
  disp_num(13, now.minute()%10);
}

void disp_num(int pos, int num){
  lcd.setCursor(pos, 0);
  lcd.write(big_num[num][0]);
  lcd.write(big_num[num][1]);
  lcd.write(big_num[num][2]);
  lcd.setCursor(pos, 1);
  lcd.write(big_num[num][3]);
  lcd.write(big_num[num][4]);
  lcd.write(big_num[num][5]);
}

void disp_colon(int pos){
  if(millis()/500%2){
    lcd.setCursor(pos,0);
    lcd.write(32);
    lcd.write(32);
    lcd.setCursor(pos,1);
    lcd.write(32);
    lcd.write(32);
  }else{
    lcd.setCursor(pos,0);
    lcd.write(6);
    lcd.write(7);
    lcd.setCursor(pos,1);
    lcd.write(6);
    lcd.write(7);
  }
}
*/