volatile char *dira,*dirc,*dirf,*dirk;
volatile char *outa,*inc,*outf,*outk;

void init_port()
{

  dira = 0x21  ; *dira = 0x0F ; outa = 0x22 ;
  dirc = 0x27  ; *dirc = 0x00 ; inc  = 0x26 ;
  dirf = 0x30  ; *dirf = 0xFF ; outf = 0x31 ;
  dirk = 0x107 ; *dirk = 0x03 ; outk = 0x108;

}


char keypad_scanning()
{
   
   volatile char row, col, key;
   for(row = 0; row < 4; row++){
    *outa = 1 << row;  
    if(*inc){ col = *inc; break;}
} 

  if(row == 0){
         if(col == 1) key = '1';
    else if(col == 2) key = '2';
    else if(col == 4) key = '3';
    else if(col == 8) key = '+';
  }
  else if(row == 1){
         if(col == 1) key = '4';
    else if(col == 2) key = '5';
    else if(col == 4) key = '6';
    else if(col == 8) key = '-';
  }
  else if(row==2){
         if(col == 1) key = '7';
    else if(col == 2) key = '8';
    else if(col == 4) key = '9';
    else if(col == 8) key = '*';
  }
  else if(row == 3){
         if(col == 1) key = 'c';
    else if(col == 2) key = '0';
    else if(col == 4) key = '=';
    else if(col == 8) key = '/';
  }
  
  return key;



}


char calculation(char s1,char s2,char func){
  switch(func){
    case '+' :return(s1+s2);
    case '-' :return(s1-s2);
    case '*' :return(s1*s2);
    case '/' :return(s1/s2);
  }
  }



void outdata(char out_data){
  volatile char *portf_data = (volatile char*)0x31;
  *portf_data = out_data;
}

void outcontrol(char out_data){
  volatile char *portk_data = (volatile char*)0x108;
  *portk_data = out_data;
}

void write_string(char*ptr){
  while(*ptr != 0){
  write_data(*ptr);
  ptr++;
  }
 }

void init_lcd(void){
  outdata (0x38);  // 8-bit mode
  lcd_control_write();  // ENABLE
  outdata (0x0F); // display blinking cursor
  lcd_control_write();  //ENABLE
  outdata(0x01);// CLEAR DISPLAY
  lcd_control_write();//ENABLE
  outdata(0x06);// auto increment
  lcd_control_write();//ENABLE

}

void write_data(char wr_data){
  outdata(wr_data);
  outcontrol(0x02);
  delay1(1);
  outcontrol(0x03);
  delay1(1);
  outcontrol(0x02);
  delay1(1);
}

void lcd_control_write(void){
  outcontrol(0x01);
  delay1(1);
  outcontrol(0x00);
  delay1(1);
}

void delay1 (int count){
  volatile long i;
  while (count){
    for(i=0;i<10000;i++);
    count--;
  }
}



void setup(){
  init_port();
  init_lcd();
  volatile char key ;
  while(1)
  {
    key = keypad_scanning();
    write_data( key);
    
  }
}

void loop(){

}