keyboard creation

[Charles Steinkuehler]

Kendrick-LUG wrote:
> I was wondering if any one had an idea on how I could go about creating 
> a keyboard.  some electronic experiance.  I tryed googling but found no 
> good information.  Im intrested in making a keyboard that accepts more 
> then 3 keys input at a time.  possibly programible

A bit more detail on what you're trying to do would help us provide you 
with more specific answers...hopefully the general info below is of some 
use.

If you're making a USB keyboard, there are several microcontrollers 
avaialble with USB ports, and you simply have to program them to behave 
like a HID (human interface device) to get them to work with most 
anything that supports USB keyboards.

If you're wanting to create a PS/2 or AT keyboard, these communicate 
using a 2 signal (clk and data) serial protocol, typically 'bit-banged' 
by the microcontroller, but some parts have hardware support to offload 
part of this.  Once you get basic communications going, you need to 
implement the high-level keyboard controller protocol (ie: emit the 
proper scan codes and responses to commands sent by the PC-side 
keyboard-controller).

I think docs for all this should be available online.  I designed a PC 
PS/2 keyboard controller part into a custom system once, and it came 
with lots of details on how everything worked.  The old IBM reference 
manuals for the original PC and AT would probably also cover this.  I've 
also found the BIOS manufactures to provide good documentation on 
low-level system stuff, so you might check them out, as well.

-- 
Charles Steinkuehler
charles at steinkuehler.net