ds3231.ino

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

// 1. Initialize the LCD (Address 0x27 is standard, 16 columns, 2 rows)
// If your screen is blank, change 0x27 to 0x3F
LiquidCrystal_I2C lcd(0x27, 16, 2);

// 2. Initialize the RTC module
RTC_DS3231 rtc;

void setup() {
  // Start I2C communication
  Wire.begin();
  
  // Start the LCD
  lcd.init();
  lcd.backlight();
  
  // Start the RTC
  if (!rtc.begin()) {
    lcd.print("RTC Not Found!");
    while (1); // Halt if hardware is disconnected
  }

  // --- THE PRODUCTION GATEKEEPER ---
  // This checks if the RTC lost power (battery failure or first time use)
  if (rtc.lostPower()) {
    lcd.clear();
    lcd.print("Setting Time...");
    
    // Sets the RTC to the date & time this sketch was compiled
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
    
    delay(2000); 
    lcd.clear();
  } 
  // If rtc.lostPower() is false, the code skips the adjustment 
  // and keeps the real-time running from the battery.
}

void loop() {
  // Get the current time from the RTC chip
  DateTime now = rtc.now();

  // Display Date on Top Row (Line 0)
  lcd.setCursor(0, 0);
  lcd.print("Date: ");
  if (now.day() < 10) lcd.print('0');
  lcd.print(now.day());
  lcd.print('/');
  if (now.month() < 10) lcd.print('0');
  lcd.print(now.month());
  lcd.print('/');
  lcd.print(now.year());

  // Display Time on Bottom Row (Line 1)
  lcd.setCursor(0, 1);
  lcd.print("Time: ");
  printDigits(now.hour());
  lcd.print(':');
  printDigits(now.minute());
  lcd.print(':');
  printDigits(now.second());

  delay(1000); // Update the screen every 1 second
}

// Helper function to keep the layout clean (adds leading zeros)
void printDigits(int digits) {
  if (digits < 10) {
    lcd.print('0');
  }
  lcd.print(digits);
}