Keyboard

[Andr3w]

Hello!



I'm making a small kernel for my OS (working in PMode).

I'm trying to make a keyboard driver.

Could you help me and answer why this code isn't working?

Code: Select all

	mov word[ds:(9*4)  ], keyboard_handler    
	mov word[ds:(9*4)+2], 0                  

	jmp $
keyboard_handler:
  	pusha
  	in  al, 0x60

  	call write_byte_as_hex
	mov bl, '|'
	call Putch32
  	mov al, 0x20
  	out 0x20, al
 
  	popa
	iret
 
hex_chars: db '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'

write_byte_as_hex:
  	pusha
  	and  ax, 0xFF
  	push ax
  	mov  bx, ax
  	shr  bx, 4
  	mov  bl, [hex_chars+bx]
	call Putch32
  	pop  bx
  	and  bx, 0xF
  	mov  bl, [hex_chars+bx] 
	call Putch32
  	popa
	ret

P.S Putch32 function puts a char from BL register on the screen.

Thanks!

[Combuster]

You are running real mode code in protected mode.

[kop99]

when your key pressed, keyboard handler is called?

[CmpXchg]

That's not gonna work, mate
How about setting up IVT?

[Troy Martin]

How about setting up IVT?

In protected mode? Haha, more like remapping the PIC and setting up the ever-tricky (for noobs) IDT. Th' Interrupt Vector Table is for real mode, the Interrupt Descriptor Table is for protected mode.

The answer is on the wiki. RTFM.

[cyr1x]

Th' Interrupt Vector Table is for real mode, the Interrupt Descriptor Table is for protected mode.

It's the same thing in both RM and PM. These are only different names, while IVT is the more general term, IDT is the x86-specific term.

[yemista]

Th' Interrupt Vector Table is for real mode, the Interrupt Descriptor Table is for protected mode.

It's the same thing in both RM and PM. These are only different names, while IVT is the more general term, IDT is the x86-specific term.

Well the idea is the same, but IVT exists in memory by the BIOS setting it up. IDT needs to be setup differently because of the larger address space available, but they basically work the same. Try this link for more information: http://osdever.net/tutorials/interrupts.3.php

[mathematician]

Hello!



I'm making a small kernel for my OS (working in PMode).

I'm trying to make a keyboard driver.

Could you help me and answer why this code isn't working?

Code: Select all

	mov word[ds:(9*4)  ], keyboard_handler    
	mov word[ds:(9*4)+2], 0                  

	jmp $
keyboard_handler:
  	pusha
  	in  al, 0x60

  	call write_byte_as_hex
	mov bl, '|'
	call Putch32
  	mov al, 0x20
  	out 0x20, al
 
  	popa
	iret
 
hex_chars: db '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'

write_byte_as_hex:
  	pusha
  	and  ax, 0xFF
  	push ax
  	mov  bx, ax
  	shr  bx, 4
  	mov  bl, [hex_chars+bx]
	call Putch32
  	pop  bx
  	and  bx, 0xF
  	mov  bl, [hex_chars+bx] 
	call Putch32
  	popa
	ret

P.S Putch32 function puts a char from BL register on the screen.

Thanks!

You need to go to Intel or AMD's site and download their system programming manuals. There you will find out all about protected mode interrupt descriptor tables. Also, if you are writing a full blown kernel, you might want to reprogram the PIC to something other than int 9 for the keyboard controller. The first 32 interrupts are reserved by Intel - something IBM thought they could ignore when they developed the first PC - but in these days of protected mode operating systems, it can be ignored no longer.

[jal]

The first 32 interrupts are reserved by Intel - something IBM thought they could ignore when they developed the first PC - but in these days of protected mode operating systems, it can be ignored no longer.

They didn't entirely ignore that: IRQ0 is mapped to INT8. The 8086 used only a few interrupts (NMI, BRK, INTO). Not until the 80186 and later the 80286, 386 more processor interrupts / acceptions became available. By then, it was too late to change anything or about all software would break (keyboard and timer hooks, anyone?).


JAL