I am writing a tiny OS as part of an assigment for school,but I got stuck when it comes to get keyboard input (press a key -> display it on screen). I am using the Bare Bones tutorial from osdev.org (gcc cross-compiler, GRUB bootloader, ld linker) and since I am in protected mode I can not use BIOS interrupts for input, that's why I have to write my own interrupt handler (?) but I'm not sure how to do that even after I read some osdev articles and forum discussions. Very similar problem (http://forum.osdev.org/viewtopic.php?f=1&t=9746) except that I don't know how to "set up the interrupts".
#if !defined(__cplusplus)
#include <stdbool.h> /* C doesn't have booleans by default. */
#endif
#include <stddef.h>
#include <stdint.h>
#define INT_DISABLE 0
#define INT_ENABLE 0x200
#define PIC1 0x20
#define PIC2 0xA0
#define ICW1 0x11
#define ICW4 0x01
void outb( unsigned short port, unsigned char val )
{
asm volatile("outb %0, %1" : : "a"(val), "Nd"(port) );
}
static __inline unsigned char inb (unsigned short int port)
{
unsigned char _v;
__asm__ __volatile__ ("inb %w1,%0":"=a" (_v):"Nd" (port));
return _v;
}
void init_pics(int pic1, int pic2)
{
/* send ICW1 */
outb(PIC1, ICW1);
outb(PIC2, ICW1);
/* send ICW2 */
outb(PIC1 + 1, pic1);
outb(PIC2 + 1, pic2);
/* send ICW3 */
outb(PIC1 + 1, 4);
outb(PIC2 + 1, 2);
/* send ICW4 */
outb(PIC1 + 1, ICW4);
outb(PIC2 + 1, ICW4);
/* disable all IRQs */
outb(PIC1 + 1, 0xFF);
}
/*irrelevant code*/
#if defined(__cplusplus)
extern "C" /* Use C linkage for kernel_main. */
#endif
void kernel_main()
{
terminal_initialize();
char c;
init_pics(0x20, 0x28);
c = inb(0x60);
terminal_putchar(c);
}
This is printing me a white box.If I try listening to port 0x64 I get some different character. I don't expect this to work, because I don't have the interrupt. I think it should be something like
void _interrupt button_pressed()
{
/*code*/
}
if(button_pressed)
{
c = inb(0x60);
//code to translate the char to ASCII
terminal_putchar(asciiChar);
}
Any help is appreciated. Thanks