Bis 99 zählen

const int COUNT_DELAY_MS = 1000;
const int DELAY_MS = 5;
const int SEGMENT_PIN[] = { 8, 7, 6, 5, 4, 3, 2 };
const int SEGMENT_PIN_COUNT = 7;
const int DISPLAY_PIN[] = { 9, 10 };
const int DISPLAY_PIN_COUNT = 2;
 
const byte DIGIT[] = {
//    abcdefg
    B01111110, // 0
    B00110000, // 1
    B01101101, // 2
    B01111001, // 3
    B00110011, // 4
    B01011011, // 5
    B01011111, // 6
    B01110000, // 7
    B01111111, // 8
    B01111011  // 9
};
const int DIGIT_COUNT = 10;
byte number;
unsigned long nextCount;
 
void setup() {
    int i = 0;
    while (i < SEGMENT_PIN_COUNT) {
        pinMode(SEGMENT_PIN[i], OUTPUT);
        i = i + 1;
    }
 
    i = 0;
    while (i < DISPLAY_PIN_COUNT) {
        pinMode(DISPLAY_PIN[i], OUTPUT);
        i = i + 1;
    }
 
    number = 0;
    nextCount = millis() + COUNT_DELAY_MS;
}
 
void showByte(byte b) {
    byte i = 0;
    while (i < SEGMENT_PIN_COUNT) {
        if ((b & (1 << i)) != 0) {
            digitalWrite(SEGMENT_PIN[i], HIGH);
        }
        else {
            digitalWrite(SEGMENT_PIN[i], LOW);
        }
 
        i = i + 1;
    }
}
 
void loop() {
    // Display 0 einschalten (LOW), 1 ausschalten (HIGH)
    digitalWrite(DISPLAY_PIN[0], LOW);
    digitalWrite(DISPLAY_PIN[1], HIGH);
    showByte(DIGIT[number % 10]);
    delay(DELAY_MS);
    // Display 0 ausschalten (HIGH), 1 einschalten (LOW)
    digitalWrite(DISPLAY_PIN[0], HIGH);
    digitalWrite(DISPLAY_PIN[1], LOW);
    showByte(DIGIT[(number / 10) % 10]);
    delay(DELAY_MS);
 
    unsigned long now = millis();
    if (nextCount <= now) {
        number = number + 1;
        if (number > 99) {
          number = 0;
        }
 
        nextCount = now + COUNT_DELAY_MS;
    }
}