void show_number(unsigned char segment,unsigned char number);
void show(int num);
void show_number(unsigned char segment,unsigned char number)
{    
   switch(segment)
      {
      case 1:seg_1;break;
      case 2:seg_2;break;
      case 3:seg_3;break;
      case 4:seg_4;break;
      default: seg_1;break;
      }                      
   switch(number)        
      {
      case 0:port_data=~63;break;
      case 1:port_data=~6;break;
      case 2:port_data=~91;break;
      case 3:port_data=~79;break;
      case 4:port_data=~102;break;
      case 5:port_data=~109;break;
      case 6:port_data=~125;break;
      case 7:port_data=~7;break;
      case 8:port_data=~127;break;
      case 9:port_data=~111;break;
      default:port_data=~63;break;      
      }  
}

//seven_seg.h
//LED segments
#define    LA    0x01    // 1
#define    LB    0x02    // 2
#define    LC    0x04    // 4
#define    LD    0x08    // 8
#define    LE    0x10    // 16
#define    LF    0x20    // 32
#define    LG    0x40    // 64
#define    LH    0x80    //128
//Seven Segment Signs
#define    SS_0    LA | LB | LC | LD | LE | LF
#define    SS_1         LB | LC
#define    SS_2    LA | LB      | LD | LE         | LG
#define    SS_3    LA | LB | LC | LD             | LG
#define    SS_4         LB | LC            | LF    | LG
....
//seven_seg.c
typedef struct _decode_table
    {
    BYTE ss;
    BYTE ch;
    } decode_table;
    
const decode_table ss_table[] =     
{
    {SS_0,'0'},
    {SS_1,'1'},
    {SS_2,'2'},
    {SS_3,'3'},
....
void OutLED(char* str)
{
for(BYTE i=0; i<DISPLAY_X; i++ )
    {
    led_buf[i] = char2SS(str[i]);
    }
}
...
BYTE char2SS(BYTE b)
{
for(BYTE i = 0; i < sizeof(ss_table)/sizeof(decode_table); i++)
    {
    if(b == ss_table[i].ch)
        {
        return ss_table[i].ss;
        }
    }
return SS_USC;
}
...
//это запускается по таймеру
void UpdateDisplay(void)
{
kbd_timer++;
OffSegment();
OffCommon();
OutSegment(led_buf[pos]);
OutPoint();
OutCommon(pos);
if(kbd_timer > 70)
    {
    CheckKBD();
    kbd_timer = 0;
    }
pos++;
if(pos == DISPLAY_X)
    {
    pos = 0;
    }
}
...
//а это ARMовский код, но идея должна быть понятна
void OffSegment(void)
{
AT91F_PIO_SetOutput(AT91C_BASE_PIOA,(0xff << SEG_A));  
}
//--------------------------------------------------------------------------
void OffCommon(void)
{
AT91F_PIO_SetOutput(AT91C_BASE_PIOA,(0x0f << COM0));
}
//--------------------------------------------------------------------------
void OutSegment(BYTE s)
{
AT91F_PIO_ClearOutput(AT91C_BASE_PIOA,(s << SEG_A));
}
//--------------------------------------------------------------------------
void OutCommon(BYTE p)
{
AT91F_PIO_ClearOutput(AT91C_BASE_PIOA,(1 << (COM0 + p)));
}
//--------------------------------------------------------------------------
void OutPoint(void)
{
if(dec_point > DISPLAY_X)
    {
    AT91F_PIO_SetOutput(AT91C_BASE_PIOA,(1 << SEG_H));
    }
if(dec_point == pos)
    {
    AT91F_PIO_ClearOutput(AT91C_BASE_PIOA,(1 << SEG_H));
    }
}