#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 32 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Button pins
const int buttonUpPin = 2;
const int buttonDownPin = 3;

// BCD output pins
const int bcdPins[4] = {4, 5, 6, 7};

// Variable to store the current number
int currentNumber = 0;

void setup() {
  // Initialize OLED display
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { 
    for(;;); // Don't proceed, loop forever
  }
  display.clearDisplay();
  display.setTextSize(5);      
  display.setTextColor(SSD1306_WHITE);  
  display.setCursor(0,0);     

  // Initialize button pins
  pinMode(buttonUpPin, INPUT_PULLUP);
  pinMode(buttonDownPin, INPUT_PULLUP);

  // Initialize BCD output pins
  for (int i = 0; i < 4; i++) {
    pinMode(bcdPins[i], OUTPUT);
  }

  updateDisplay();
}

void loop() {
  if (!digitalRead(buttonUpPin)) {
    currentNumber++;
    if (currentNumber > 9) currentNumber = 0;
    updateDisplay();
    delay(200); // Debounce delay
  }

  if (!digitalRead(buttonDownPin)) {
    currentNumber--;
    if (currentNumber < 0) currentNumber = 9;
    updateDisplay();
    delay(200); // Debounce delay
  }
}

void updateDisplay() {
  display.clearDisplay();
  display.setCursor(0,0);
  display.print(currentNumber);
  display.display();

  // Update BCD output
  for (int i = 0; i < 4; i++) {
    if (currentNumber & (1 << i)) {
      digitalWrite(bcdPins[i], LOW); // Representing GND
    } else {
      digitalWrite(bcdPins[i], HIGH); // Representing not connected (n/c)
    }
  }
}