// 74HC595 shift register pins
const int dataPin = 11;
const int latchPin = 8;
const int clockPin = 12;

// Digit control pins (to enable left/right 7-segment display)
const int digit1Pin = 9;
const int digit2Pin = 10;

// const int dataPin = 2;   // DS to D2
// const int clockPin = 3;  // SHCP to D3
// const int latchPin = 4;  // STCP to D4
// const int digit1Pin = 5; // Tens digit control (D5)
// const int digit2Pin = 6; // Units digit control (D6)

// Segment patterns for 0-9 (Common Cathode: LSBFIRST)
const byte digitPatterns[10] = {
  B00111111, // 0
  B00000110, // 1
  B01011011, // 2
  B01001111, // 3
  B01100110, // 4
  B01101101, // 5
  B01111101, // 6
  B00000111, // 7
  B01111111, // 8
  B01101111  // 9
};

void setup() {
  Serial.begin(9600);
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(digit1Pin, OUTPUT);
  pinMode(digit2Pin, OUTPUT);
  digitalWrite(digit1Pin, LOW);
  digitalWrite(digit2Pin, LOW);
}

void loop() {
  static int count = 0;
  
  // Display current count for 1 second
  unsigned long startTime = millis();
  while (millis() - startTime < 1000) {
    displayNumber(count);
  }
  
  count = (count + 1) % 100; // Increment count (0-99)
  Serial.println(count);
}

void displayNumber(int number) {
  int tens = number / 10;
  int units = number % 10;

  // Display tens digit
  digitalWrite(digit2Pin, HIGH);       // Turn off units
  digitalWrite(latchPin, HIGH);
  shiftOut(dataPin, clockPin, MSBFIRST, digitPatterns[tens]);
  digitalWrite(latchPin, LOW);
  digitalWrite(digit1Pin, LOW);      // Turn on tens
  delay(5);                           // Adjust for brightness

  // Display units digit
  digitalWrite(digit1Pin, HIGH);       // Turn off tens
  digitalWrite(latchPin, HIGH);
  shiftOut(dataPin, clockPin, MSBFIRST, digitPatterns[units]);
  digitalWrite(latchPin, LOW);
  digitalWrite(digit2Pin, LOW);      // Turn on units
  delay(5);
}