Very very simple keyboard input?

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Giedrius

Joined: 13 Feb 2005
Posts: 40
Location: Lithuania

Giedrius 06 Apr 2005, 08:33

Can someone give me an example of simple, but very fast way to get a pressed button. I've searched, but found only complex ways of doing it, some ways were too slow and some didn't work...

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06 Apr 2005, 08:33

gunblade

Joined: 19 Feb 2004
Posts: 209

gunblade 06 Apr 2005, 09:59

Code:

mov ah, 8 ;non echoed input
int 21h

; al now equals the character pressed

use mov ah, 1 if you want the input character to be echoed

06 Apr 2005, 09:59

Giedrius

Joined: 13 Feb 2005
Posts: 40
Location: Lithuania

Giedrius 06 Apr 2005, 13:01

Thanks. But I need it to be accessed directly (so the program can continue working if no button was pressed) I don't know if there's a simple way of doing that... Confused

And I need it to be as fast as it can be.

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06 Apr 2005, 13:01

Matrix

Joined: 04 Sep 2004
Posts: 1166
Location: Overflow

Matrix 06 Apr 2005, 16:52

Hello
please go here

there is no simpler way to read keyboard directly,

if you're willing to use interrupts, it will be very slow.
speed - method
fast - directly via keyboard port
slow - via bios keyboard handling interrupt
very slow - via dos keyboard handling

06 Apr 2005, 16:52

Giedrius

Joined: 13 Feb 2005
Posts: 40
Location: Lithuania

Giedrius 06 Apr 2005, 17:00

That's what I was trying to get to work... It didn't work. Maybe I should try again...

06 Apr 2005, 17:00

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 09 Apr 2005, 17:00

Why not do this:

Code:

        xor   ax,ax        in    AL,60h         test  al,10000000b        jnz   NoKey; Yes a key has been pressed, do some thing hereNoKey:;Carry on with the loop here, as no key pressed

let me know if it for a game.

09 Apr 2005, 17:00

Giedrius

Joined: 13 Feb 2005
Posts: 40
Location: Lithuania

Giedrius 10 Apr 2005, 10:29

I don't know if you can call it a game, but it needs to be fast. It has significant speed decrease when using your code... I only need it to exit when a key was pressed. Or there's no faster way than this one?

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10 Apr 2005, 10:29

f0dder

Joined: 19 Feb 2004
Posts: 3175
Location: Denmark

f0dder 10 Apr 2005, 11:35

You could set up an interrupt handler for the keyboard IRQ, and handle keys on interrupt rather than keep polling...

10 Apr 2005, 11:35

Giedrius

Joined: 13 Feb 2005
Posts: 40
Location: Lithuania

Giedrius 10 Apr 2005, 13:57

Maybe you could give me an example, or lead me to some guide? I don't know much about assembly programming yet... Confused

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10 Apr 2005, 13:57

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 10 Apr 2005, 17:22

This will replace Dos keyboard interrupt, for yours (call this bit, at start of program)

Code:

MOV     AL,09h                    ; Get INT 09h addressMOV     AH,35hINT     21hMOV     [oldint9],BX              ; Save it for laterMOV     [oldint9+2],ESMOV     AL,09h                    ; Set new INT 09hMOV     DX,Newint9        ; DS:DX = new interruptMOV     AH,25hINT     21h

This is you new interrupt so do what needs to be done on key press here;

Code:

Newint9: pusha   ;Do some thing here       mov     al, 0x20out     0x20, al        ; If you do something like, jump exit do it here, after the above code.     popaIRET

This needs calling at end of program

Code:

ReStoreInt9:MOV     AL,09h                    ; Restore original INT 09hMOV     DX,[oldint9]MOV     DS,[oldint9+2]            ; Move old INT 09H pointer to DS:DXMOV     AH,25hINT     21hRET

Note: Most of this code is from a TASM Game, i wrote, so may need converting to FASM.
You will need to set up var for saving "old INT 09H " eg:
oldint9 dd 0

10 Apr 2005, 17:22

Giedrius

Joined: 13 Feb 2005
Posts: 40
Location: Lithuania

Giedrius 10 Apr 2005, 17:45

Thank you!! Very Happy

Where is the button code stored in the interrupt? And could you explain me what does mov al, 0x20 out 0x20, al do?

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10 Apr 2005, 17:45

Dex4u

Joined: 08 Feb 2005
Posts: 1601
Location: web

Dex4u 10 Apr 2005, 18:20

When you press a key a interrupt is generated, which jump from your program to some code to deal with the IRQ, at the end of a IRQ you do the above code, so it now its the end.

As for the button code, i left it out as you said you only need to exit on keypress so soon as a key is press it jump to that code, you could try something like this ?

Code:

Newint9: call     Newint9ajmp    exitret

Code:

Newint9a:pusha   ;Do some thing here       mov     al, 0x20out     0x20, al        ; If you do something like, jump exit do it here, after the above code.     popaIRET

I do not know if it will work as its a long time since using dos. at the exit lable you need to call ReStoreInt9 before exiting.

10 Apr 2005, 18:20

Giedrius

Joined: 13 Feb 2005
Posts: 40
Location: Lithuania

Giedrius 10 Apr 2005, 18:34

I've done everything that I wanted. Thanks. I only asked for some explanation about it.

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10 Apr 2005, 18:34

bubach

Joined: 17 Sep 2004
Posts: 341
Location: Trollhättan, Sweden

bubach 11 Apr 2005, 06:32

Code:

mov     al, 0x20
out     0x20, al

on my forum, Dex4u wrote:

There are two types of interrupts a software and a hardware, when you write a "int 21h" you get a software int and when a key is pressed you get a hardware int.

A interrupt causes the procsseeor to suspend the current operation and act on the reason for the interruption, 8259 masks all further interrupts from that device until is receives an end of interrupt signal from the interrupt service routine( that is the above code). Once the interrupt has been handled, it returns to the interrupted program.

And how to actually get the scancodes? Do like this:

Code:

          xor     eax, eax           ; clear eax
          in      al, 0x60             ; mov scan-code into al

          test    al, 0x80            ; check if it was a press or a release
          jnz     .key_up

                                         ; check diffrent keys here:
          cmp     al, 42             ; this checks for a press on the left shift
          jnz     .check_next      ; nope, that wasn't pressed, check next

      .key_up:

11 Apr 2005, 06:32

Dilshod

Joined: 23 Feb 2005
Posts: 23
Location: Uzbekistan, Tashkent

Dilshod 12 Apr 2005, 09:44

Try this:

Code:

    mov   ah,1
    int      16h
    jz       .NoKeyPressed
    mov    ah,0
    int       16h
    ;...
    ;... KeyCode in AX, AL-ASCII, AH-Scan
    ;...
.NoKeyPressed:

12 Apr 2005, 09:44

vid
Verbosity in development

Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia

vid 12 Apr 2005, 11:37

http://www.qzx.com/pc-gpe/keyboard.txt

12 Apr 2005, 11:37

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