Why isn't my keyboard handler working?

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StringCheesian

Joined: 20 Feb 2004
Posts: 20

StringCheesian 28 Feb 2004, 04:45

I made my keyboard int handler put an 'A' on the screen whenever a key is pressed, but I'm not seeing an A... and I'm stumped. This is my first protected mode interrupt handler, so I could doing something wrong.

The whole file is less than 2 kb, but I didn't know if it would be annoying to post that much text, so I attached it.

Here's the keyboard int handler:

Code:

keyboardIntHandler:
   push eax
   push ebx
   push ds

   mov  eax, dataSel
   mov  ds, eax

   ; A grey-on-blue 'A' should appear at (1,0) on the
   ;   screen as soon as a key is pressed:
   mov  al, 'A'
   mov  ah, 0x17
   mov  [0xB8002], ax

   ; Update the key state map:
   xor  eax, eax
   mov  bl, 1
   in   al, 60h
   test al, 80h
   jz   byte @F
     and  al, 7Fh
     dec  bl
   @@:
   mov  [keyStateMap+eax], bl

   pop  ds
   pop  ebx
   pop  eax

   iretd

Description:		Download
Filename:	kernel.asm
Filesize:	1.67 KB
Downloaded:	672 Time(s)

28 Feb 2004, 04:45

Ralph

Joined: 04 Oct 2003
Posts: 86

Ralph 28 Feb 2004, 05:45

Hi. You need to wait for input. Your routine will just grab whatever is currently in there and not actually wait for you to enter a key. Try something like this:

Code:

     .read_key:
           in    al,64h
           and   al,01h
           jz   .read_key
     in    al,60h

al will contain the scancode. In my keyboard driver I then just use xlat to convert to whatever ASCII key it is.

28 Feb 2004, 05:45

StringCheesian

Joined: 20 Feb 2004
Posts: 20

StringCheesian 28 Feb 2004, 06:26

Thanks, that probably would have causes a lot of problems later.

But it's still acting like the interrupt is never being called...

EDIT: INT 9 gets called whenever a key is pressed, just like in real mode, right? Or do I have to poll for input?

28 Feb 2004, 06:26

0x4e71

Joined: 25 Feb 2004
Posts: 50

0x4e71 28 Feb 2004, 11:56

Well, did you enable IRQ1 and did you enable interrupts? otherwise, when initializing, add something like :

Code:

  mov ax,$FFFd ; enable irq 1 only
    out $21,al
  mov al,ah
   out $A1,al
  sti

Also, at the bottom of your handler you have to tell the PIC you are done with IRQ1, so:

Code:

      mov al,$20
  out $20,al

Cheers,
-Luigi

28 Feb 2004, 11:56

StringCheesian

Joined: 20 Feb 2004
Posts: 20

StringCheesian 29 Feb 2004, 05:01

Yey, it works! Now I wish I understood why it works: what's an IRQ?

29 Feb 2004, 05:01

0x4e71

Joined: 25 Feb 2004
Posts: 50

0x4e71 29 Feb 2004, 11:37

sure.
read
http://www.osdever.net/tutorials/irqs.php?the_id=37

and many other tutorials at osdever.net

29 Feb 2004, 11:37

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