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XT keyboard to AT motherboard adapter ?

soviet9922

soviet9922

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Jun 12, 2013
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Montevideo, Uruguay
Hi guys, anyone knows about any adapter that let me use an XT keyboard on an AT motherboard ?.
Available for sale or if there no one maybe project using a pic y can do myself ?.
 
You may have to do that one yourself, given that many fewer PC XT keyboards have survived than AT/PS2 ones. Any 5V MCU should do the job. An Arduino would have more than enough processing power. There's plenty of code out there that shows how to interface with a PS2 keyboard; the XT keyboard's protocol is much, much simpler.
 
I don't see any particular reason why you couldn't fit the code into an 8-pin PIC. Even the 12F629 that I used in the original XTATKEY project used only about half the code memory space available.

You can ignore some of the PC-to-keyboard commands, as there are no LEDs on the XT keyboard. You will have to figure out what to do about the missing F11 and F12 keys, as well as the rigtht Alt and Ctrl keys (some applications differentiate between left and right keys of the same name).
 
No, you have it right--there are many more AT and PS/2 keyboards out there and too few XT keyboards. So the little converter allows use of an AT keyboard on an XT, not vice-versa.

But the code might give you some ideas, since the converter has to process PS/2 keyboard messages--at least you can get an idea of what's involved. In my opinion, handling a PS/2 keyboard, translating to the relatively simple XT protocol is quite a bit harder than doing the reverse. But that's just a back-of-the-envelope guess.
 
If it is an early AT clone motherboard, there is a possibility it will work with the XT keyboard anyway. There are a few with jumper settings, and I guess perhaps some are automatic. But I would say the chances are slim. What motherboard are you trying to connect it to? What is the keyboard manufacture? If they're both IBM then none of this applies.
 
I have 5 possible motherboards x2 286 and a early 386 one will post some pictures of them maybe you can help me identify the jumpers ?

Also i was pointed by an ebay keyboard adapter seller to this thread:
https://deskthority.net/keyboards-f2/xt-to-ps-2-converter-for-model-f-t11474.html

This guy have done exactly what i'm looking for an adapter for the ibm portable keyboard XT to AT.
Maybe if im lucky he still are selling them because the shematic don't seem to be available.
 
You can just about suss out the schematic--the MCU has only 8 pins and you know which ones are power and ground. He includes a couple of LEDs, which aren't really needed. So you've got a pullup resistor and a couple of diodes. Not that much different from my PIC implementation--although I did include a decoupling capacitor (just good design when you have something on a cable).

What would be more interesting would be the source code.
 
Thanks for the help, looking in my parts bin found one of this:
http://stason.org/TULARC/pc/motherboards/W/WESTERN-DIGITAL-CORPORATION-286-WD286-WDM20.html
This one have a xt jumper and work great on the ibm portable keyboard.
Lots of options in this motherboard i found it some months ago on a flea market.
Also the designer of the XT to AT adapter for the ibm portable keyboard Engicoder from deskthority.net say that he will mail me a pcb for the adapter, and will provide me the binary for the pic ic.
 
Glad you got it all working. Is the binary for the converter open source?
 
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