counter_ardunio.cpp

int A = 8;
int B = 9;
int C = 10;
int D = 11;
int E = 12;
int F = 13;
int G = 6;
int H = 7;

int D1 = 2;
int D2 = 3;
int D3 = 4;
int D4 = 5;

int BTN = 0;
int BTN2 = 1;

int DS[4] = {D1, D2, D3, D4};
int POW10[4] = {1000, 100, 10, 1};

int DELAY = 55;

class DigitalDisplay {
public:
  int n;

  DigitalDisplay() :
    n(0)
  {
    pinMode(A, OUTPUT);
    pinMode(B, OUTPUT);
    pinMode(C, OUTPUT);
    pinMode(D, OUTPUT);
    pinMode(E, OUTPUT);
    pinMode(F, OUTPUT);
    pinMode(G, OUTPUT);
    pinMode(H, OUTPUT);
    
    pinMode(D1, OUTPUT);
    pinMode(D2, OUTPUT);
    pinMode(D3, OUTPUT);
    pinMode(D4, OUTPUT);
    
    for (int i = 0; i < 4; i += 1) {
      digitalWrite(DS[i], HIGH);
    }
  }
  
  void writeDigit(int i) {
    bool a, b, c, d, e, f, g;
    
    a = i == 2 || i == 3 || (i >= 5 && i <= 9) || i == 0;
    b = (0 <= i && i <= 4) || (7 <= i && i <= 9);
    c = i >= 0 && i != 2;
    d = i == 0 || i == 2 || i == 3 || i == 5 || i == 6 || i == 8 || i == 9;
    e = i == 0 || i == 2 || i == 6 || i == 8;
    f = i == 0 || (4 <= i && i <= 6) || i == 8 || i == 9;
    g = (2 <= i && i <= 6) || i == 8 || i == 9;
    
    digitalWrite(A, a);
    digitalWrite(B, b);
    digitalWrite(C, c);
    digitalWrite(D, d);
    digitalWrite(E, e);
    digitalWrite(F, f);
    digitalWrite(G, g);
  }
  
  void draw() {
    for (int i = 3; i >= 0; i -= 1) {
      digitalWrite(DS[i], LOW);
      
      if (n >= POW10[i] || (n == 0 && i == 3)) {
        int digit = (n / POW10[i]) % 10;
        writeDigit(digit);
      } else {
        writeDigit(-1);
      }
      
      delay(2);
      writeDigit(-1);
      digitalWrite(DS[i], HIGH);
    }
  }
  
  void setNumber(int n) {
    this->n = n;
  }
};

DigitalDisplay disp;

void setup() {
  pinMode(BTN, INPUT);
  pinMode(BTN2, INPUT);
  disp.setNumber(0);
}

void loop() {
  int cnt = 0;
  bool last1 = false, last2 = false;
  
  while (true) {
    bool btn1 = digitalRead(BTN) == LOW,
         btn2 = digitalRead(BTN2) == LOW;
    
    if (btn1 != last1 && !btn1) {
      cnt += 1;
    }
    
    if (btn2 != last2 && !btn2) {
      cnt -= 1;
    }
    
    disp.setNumber(cnt);
    
    last1 = btn1;
    last2 = btn2;
    
    disp.draw();
  }
}