A simple single digit seven segment display

Other Hardware LEDs and Multiplexing
20

With that out of the way, you can write a fairly simple display routine:

volatile unsigned char led_buffer[DIGS_MAX]; //display buffer. DIGS_MAX defines the max number of led digits allowed

void led_display(void) {
  static unsigned char dig=0; //digital counter

  dig += 1; //increment the digit
  if (dig == DIGS_MAX) dig = 0; //reset dig if max digit has been reached

  //turn off all digits
  DIG_OFF(DIG0); DIG_OFF(DIG1); ...

  SEGs_OUT(led_buffer[dig]); //send out segment information

  //turn on the digit
  //can be implemented more cleanly with an array
  switch (dig) {
    case 0: DIG_ON(DIG0); break;
    case 1: DIG_ON(DIG1); break;
  ...
  }
}

So each time, led_display() is called, it displays a number on the led.