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

RTC_DS3231 rtc;

// Define the pins for the 74HC595 shift register
const int dataPin = 4;  // DS (data pin)
const int clockPin = 5; // SHCP (clock pin)
const int latchPin = 6; // STCP (latch pin)

// Define the segment pins
const int segmentPins[] = {7, 8, 9, 10, 11, 12, 13};

void setup() {
  Wire.begin();
  rtc.begin();

  // Set the shift register pins as outputs
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);

  // Set the segment pins as outputs
  for (int i = 0; i < 7; i++) {
    pinMode(segmentPins[i], OUTPUT);
  }

  // Uncomment the following line if you want to set the time on the RTC
  // rtc.adjust(DateTime(__DATE__, __TIME__));
}

void loop() {
  DateTime now = rtc.now();
  
  int hour = now.hour();
  int minute = now.minute();
  int second = now.second();

  // Display time on the 8-digit seven-segment display
  displayTime(hour, minute, second);

  delay(1000); // Update every second
}

void displayTime(int hour, int minute, int second) {
  byte digits[] = {
    B11111100, // Digit 0 (segment a, b, c, d, e, f)
    B01100000, // Digit 1 (segment b, c)
    B11011010, // Digit 2 (segment a, b, d, e, g)
    B11110010, // Digit 3 (segment a, b, c, d, g)
    B01100110, // Digit 4 (segment b, c, f, g)
    B10110110, // Digit 5 (segment a, c, d, f, g)
    B10111110, // Digit 6 (segment a, c, d, e, f, g)
    B11100000, // Digit 7 (segment a, b, c)
  };

  // Loop through the digits
  for (int digit = 0; digit < 8; digit++) {
    // Shift out the digit data
    shiftOut(dataPin, clockPin, MSBFIRST, digits[digit]);

    // Enable the current digit
    digitalWrite(latchPin, LOW);
    digitalWrite(segmentPins[digit], HIGH);
    digitalWrite(latchPin, HIGH);

    // Delay to display the digit
    delay(2);

    // Disable the current digit
    digitalWrite(latchPin, LOW);
    digitalWrite(segmentPins[digit], LOW);
    digitalWrite(latchPin, HIGH);
  }
}