void init_port(void);
void outport_d(char);  // 7 segment
void outport_b(char);  // keypad row
char inport_c(void);   // keypad col

int main(void){

  char numbers[11] = {0x3F, 0x06, 0x5B, 0x4F,0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x67,0x00}; // numbers[10] is off
  char x;

  init_port();
  outport_d(~(0x00));
  x = scan_keypad();

  while(1){
    
    while(x == 100){      // initial x is taken as 100 , bcz x = 0 is valid value to show on display
      x = scan_keypad();
    }
    outport_d(~(numbers[x]));
    x = 100;  //reset x
  }
}

/*--------------- PORTS CONFIG -------------------------*/

void init_port(void){

  volatile char* dird = (volatile char *)0x2A;
  volatile char* dirb = (volatile char *)0x24;
  volatile char* dirc = (volatile char *)0x27;

  *dirc = 0xF0;  // lower 4 bit input
  *dird = 0xFF;
  *dirb = 0x0F;
}

void outport_d(char data){

  volatile char* outd = (volatile char *)0x2B;
  *outd = data;
}

void outport_b(char data){

  volatile char* outb = (volatile char *)0x25;
  *outb = data & 0x0F;
}

char  inport_c(void){

  volatile char* inc = (volatile char *)0x26;
  char data;
  data = *inc & 0x0F;
  data = (~data) & 0x0F;
  return data;
}
/*-----------------------------------------*/

void delay_ms(long i){

  volatile long j;
  for(j = 0; j < 10000*i; j++);
}

char scan_keypad(void){

  char row, col , val;

  for(row = 0; row < 4; row++){

    outport_b(~(0x01 << row));
    val = inport_c();

    for(col = 0; col < 4; col++){

      if(val == (0x01 << col)){
        return (row*4 + col);
      }
    }
  }
  return 100;  // default val 100 
}