Some arduino / avr code to read a rotary encoder and drive a single 7 segment display.

stepper-encoder-7seg.ino

void setup() {
  DDRD = 0xFF;
  PORTD = 1;
  pinMode(8, INPUT);
  pinMode(9, INPUT);
}

byte digits[] = {
  0b00000011,//0
  0b11110011,//1
  0b10000101,//2
  0b00001101,//3
  0b00111001,//4
  0b01001001,//5
  0b01000001,//6
  0b00011111,//7
  0b00000001,//8
  0b00001001,//9
};

byte t = 0;
byte lastVal = 0;
byte b = 1;
byte digit = 0;

void loop() {
  PORTD = digits[digit] | ~(0x01 << b);
  b++;
  if(b > 7) {
    b = 1;
  }
  
  byte val = PINB & 0x03;
  if(val != lastVal) {
    if((val == 3 && lastVal == 2) ) {
      t++;
      if(4 == t) {
        t = 0;
        digit++;
        if(10 == digit) {
          digit = 0;
        }
      }
    } else if ((val == 2 && lastVal == 3) ) {
        if(0 == t) {
          t = 4;
          if(0 == digit) {
            digit = 10;
          }
          digit --;
        }
        t--;
    }
    lastVal = val;
  }
}