Ok,
I reallllllly need some help here .
I desperatly need to interface a 4x4 matrix keypad to a ps2 port
on a PC, the buttons will mimic some of the numeric keys
on a keyboard so no special function is needed there.
can I use a chip from an old keyboard, a PIC, or some other
IC to do this?
It will be the only keypad/keyboard device hooked to the PC,
so it needs to be able to boot of of it. I was thinking that a pic
could work somehow, or maybee salvage the insides of an
old keyboard??
Ok,
I reallllllly need some help here .
I desperatly need to interface a 4x4 matrix keypad to a ps2 port
on a PC, the buttons will mimic some of the numeric keys
on a keyboard so no special function is needed there.
ryan pogge wrote:
>
> Ok,
> I reallllllly need some help here .
> I desperatly need to interface a 4x4 matrix keypad to a ps2 port
Perhaps using a 74C922 16-key encoder chip. It give a 4 bit binary
output depending on the key pressed and a 'data available' bit as well.
Should be able to power it from the Paralel port, and it uses a single
cap for debounce.
--
Best regards
Tony
Multimedia 16F84 Beginners PIC Tools.
** NEW PicNPro Programmer and Port Interface **
Your main problem, is going to be getting the architecture to recognize
your keypad as the "Keyboard". You might be able to do that by "hooking"
the keyboard interrupts with a TSR, but that means shutting off the
keyboard in the BIOS. Alternately, you can redirect "Con" to the port you
plug the keypad into, but will again need to be able to shut off the
keyboard in the BIOS.
The chip in the keyboard, is itself an embedded controller, and the
circuit essentially maps the keyboard to a set of pins on the chip, which
then are used to determine the scan code, then sends it through a
dedicated serial port, to a standard port. Software then sends the scan
code to a companion chip on the motherboard (called the keyboard bios)
that converts it to the extended ASCII that we all love so much.
The scan code, is sent via an interrupt in the operating system, at the
bios level, and all you need to be able to do, is redirect this interrupt
to the handler you write for the port....
But what the heck, if you are going to tear down a keyboard anyway, why
not use the dedicated serial port that was meant for the keyboard, and
save yourself a little trouble?
> Ok,
> I reallllllly need some help here .
> I desperatly need to interface a 4x4 matrix keypad to a ps2 port
> on a PC, the buttons will mimic some of the numeric keys
> on a keyboard so no special function is needed there.
>
> can I use a chip from an old keyboard, a PIC, or some other
> IC to do this?
>
> It will be the only keypad/keyboard device hooked to the PC,
> so it needs to be able to boot of of it. I was thinking that a pic
> could work somehow, or maybee salvage the insides of an
> old keyboard??
>
> any ideas?
>
> Regards,
> Ryan
>
>Your main problem, is going to be getting the architecture to recognize
>your keypad as the "Keyboard". You might be able to do that by "hooking"
>the keyboard interrupts with a TSR, but that means shutting off the
>keyboard in the BIOS. Alternately, you can redirect "Con" to the port you
>plug the keypad into, but will again need to be able to shut off the
>keyboard in the BIOS.
If i use the guts of a keyboard wont this solve the problem?
>But what the heck, if you are going to tear down a keyboard anyway, why
>not use the dedicated serial port that was meant for the keyboard, and
>save yourself a little trouble?
not sure i understand.....
here is a better explanation of what i am trying to do,
I am going to be booting a PC in a car, it needs something hooked to the
PS/2
port to boot, I am running a program in place of explorer.exe shell
since it will be all that I am useing. I need to then controll that
program with a PS/2
Keyboard, HOWEVER ... the only keys I need are some of the numpad keys...
The whole keyboard is too big to fit in my car, so esentialy what i was
thinking
is to remove the case and keys from an old keyboard.... looking at which
buttons
went to which pin on the keyboard chip and just hooking a 4x4 keypad to the
apropriate pins.....
> If i use the guts of a keyboard wont this solve the problem?
> remove the case and keys from an old keyboard.... looking at which
> buttons went to which pin on the keyboard chip and just hooking a 4x4
> keypad to the apropriate pins.....
> is that going to work?
I think that is the simplest, cheapest, fastest and overall *best*
approach.
--
Cheers,
Paul B.
SHORE.INTERCOM.NET]
