gistfile1.txt

// Hardware Connections
#define R1 0xE
#define R2 0xD
#define R3 0xB
#define R4 0x7
#define C1 0x3
#define C2 0x5
#define C3 0x6

struct KeyPadCon{
   int COLS:3;
   int UNUSED:1;
   int ROWS:4;
};
struct KeyPadCon *KEYPAD=0xF81;  // Port B

// Delarations
char KeyPress(void);

// Definitions
char KeyPress(void){
   char press='@';
   KEYPAD->COLS=C1;
   switch(KEYPAD->ROWS){
      case R1:
         press='1';
         break;
      case R2:
         press='4';
         break;
      case R3:
         press='7';
         break;
      case R4:
         press='*';
         break;
      default:
   }

   KEYPAD->COLS=C2;
   switch(KEYPAD->ROWS){
      case R1:
         press='2';
         break;
      case R2:
         press='5';
         break;
      case R3:
         press='8';
         break;
      case R4:
         press='0';
         break;
      default:
   }

   KEYPAD->COLS=C3;
   switch(KEYPAD->ROWS){
      case R1:
         press='3';
         break;
      case R2:
         press='6';
         break;
      case R3:
         press='9';
         break;
      case R4:
         press='#';
         break;
      default:
   }
   return(press);
}