• Please review our updated Terms and Rules here

AT to XT Keyboard Converter

Well, I finally got around to it. I, um, dodged this up from the schematics:

Image0101.jpg

Image0102.jpg


The programmer I got from ebay worked a treat when I used it on my 486 under win95. I "tested" it today with my xt motherboard, only having some spare solid core network cable wires as a temporary solution (same wires I used building the above abomination), from the device to my board, it was a crap connection at best, but I managed to get proper responses from the LEDs, (num, caps, scroll), so even though the board reckoned there was a KB ERR, I consider it enough of a success until I get a better cable, or make one up.

So yea, I'm totally keen for a "proper" PCB run to be done again for this. :)
 
Hi! Congratulations!

Yes, another PCB run is in the works. My plan is to make an order for it along with the next batch of XT-IDE boards.

Its good to see you built your own prototype circuit! That's how it starts! :)

Thanks and have a nice day!

Andrew Lynch
 
Oh yes, I did get my ide board from you a while ago too, and after finally getting most of the electronics for it last friday, I had an afternoon soldering frenzy. I think if you're not good at soldering, you sure will be after doing that kit. :)

That I feel is how well I was able to bodge this circuit together yesterday. :)
 
I think a run of 50 PCBs for the keyboard adapters should do the trick. They are tiny enough that storage is no big deal if they don't sell quickly. I'll order up parts for another 25 of them from digikey.
 
Is here where one is supposed to file bug reports and problems?

In any case, I encountered some problems with my adapter. My setup is as following:
Victor Vicki 8088 (basically an XT clone) - adapter - PS/2 - KVM switch - PS/2 keyboard

The regular keys work fine, even including the Swedish characters ÅÄÖ. A few characters like <> and * are found at positions that perhaps resemble an XT keyboard more than an AT keyboard, but that is not a problem.

The numeric keypad also works for most of the time. I noticed the division key on the numeric board returns a minus sign just like the minus key does, but it may be a matter of misprogramming.

What does not work to satisfaction though are the cursor keys and the group of keys above: Insert, Delete, Home, End, Page Up and Page Down. All those 4 + 6 keys return numbers 0-9 just like the numeric keypad does, no matter the state of Num Lock.

I haven't checked the function keys, what codes they send. However while fiddling with the numeric keypad I noticed sometimes it manages to lock up the computer, to the point it won't accept any more input and just beeps. A soft reset Ctrl-Alt-Del however solves this, so apparently this key combination still works as expected.

Should I switch to an US keyboard layout on the XT clone and try the cursor keys again? Should I bypass the KVM and connect my keyboard directly to the adapter? Should I try an older AT style keyboard instead of PS/2? I do have some decent programmers which supposedly do most PICs and AVRs, so in case of reprogramming the chip with a newer version, I'm confident it could work.

Edit: Hm, it seems to be the same cursor key issue as Marrr reported earlier. Both of us supposedly use localized keyboard layouts, and while none of the US people seem to have noticed this before, it strikes me I definitely should try to reconfigure my XT to us an US keyboard layout for the first step of troubleshooting.
 
Last edited:
Is there any chance that some sort of keyboard.sys driver could help at this level? I've never used a driver for a keyboard before, and I don't know how back in DOS those go, but I am wondering if that might patch up some of the problems?
Otherwise, I suspect it would almost have to be something in the PIC code that is getting confused with the non US keyboard somehow. (I really don't know how the thing works, so I am absolutely talking out my ass)

I do plan on digging into this project someday down the road, and want to try and do the XT->AT converter, but you will have plenty of time to do your own debugging until that day comes where I can poke around...
 
This is interesting. I tried again tonight, and all keys except division key on the numeric keypad work like they should. Cursor keys and the other are ok. Num lock on/off works as expected. Perhaps it was something happening when I managed to lock up the keyboard buffer that caused problems before, and I should have forced a cold restart of the 8088 instead of only a soft reset. I can't say for sure the problem was in the keyboard adapter or the computer itself, but at the moment I can't spot any major problems.

In any case, it may be good news for anyone else (Marrr?) who encountered similar problems, that a clean restart and perhaps disconnecting the adapter to make sure no circuits get power and will boot up from a fresh state will solve sudden issues.
 
To handle localized keyboards with special keycodes would require custom versions of the firmware. Clearly there are differences between local versions of the XT and AT keyboard mappings.

Has anyone tried this with German, French and Cyrillic alphabet keyboards?
 
Yes, my autoexec.bat (DOS 4.01) already has "KEYB SV,,KEYBOARD.SYS" or however the syntax is. But as I posted above, the localized keys never were a problem in the first place. I can't speak for other localized keyboards though, and I suppose changing the keyboard mapping won't be accurate enough to test the adapter.
 
Hi! Last night I ordered 40 of the AT2XTKBD PCBs and they should be here in about three weeks or so. I was reordering the N8VEM DiskIO PCBs and tossed in the AT2XTKBD PCBs along with it. They are unchanged from the original with the exception of adding solder mask to the component layer for a more consistent appearance. There is no change in functionality it will just look better I think.

I don't know what the final unit price will be and need to figure that out tonight. It should be fairly inexpensive though as I just need to cover my expenses. Presuming someone takes up the PIC programming challenge, I think this PCB is also capable of XT2ATKBD operation but I suppose that remains to be seen.

As with all N8VEM PCBs this is a home brew Do It Yourself project so please bear that in mind. We're all in this together!

Thanks and have a nice day!

Andrew Lynch
 
awesome!
I recently picked up a new PIC programmer which I have yet to even plug into a machine to try it out. Provided it works, I can go ahead and buy up enough parts to assemble several of the converters. At a minimim, i will probably buy 25 of the PCBs from you so I can bulk purchase the components.
 
Hi,
I have recently acquired a cira 1990 Pro-Log industrial PC (12 MHz 286) with DOS 3.3 in ROM but without the required XT keyboard.
The AT2XT converter is exactly what I need so I have a few questions (even after reading all 193 postings!!).
Price? Still US$7 + US$5 for shipping outside the US?
Availibility? an assembeld, programmed unit is required
Payment? Mention is made of PayPal but no 'howto'
Thanks in advance for your help.
Regards,
Mike Kenny
Melbourne, Australia
 
Be certain that's what you really need--a 286 should work fine with a PS/2-type keyboard with a mini-DIN to DIN adapter. It's also possible that your motherboard has a jumper to change between XT and AT style keyboards--I have one that does.
 
Hi! The new batch of AT2XTKBD PCBs have arrived. These are the home brew "do it yourself" variety so its PCB only.

They are $5 each plus $2 shipping in the US or $5 elsewhere. Please send a PayPal to LYNCHAJ@YAHOO.COM with your correct shipping address and I send your PCBs right away!

Thanks and have a nice day!

Andrew Lynch

PS, I was going to post a photo of the new PCBs but our camera is broken and I used another one. The photo is so blurry and out of focus as to be useless so just imagine the photo in the wiki with an extra layer of solder mask on the top of the PCB. (hint: its more green colored)
 
Last edited:
Hi! Thanks! Wow! I just checked my stash of AT2XTKBD PCBs and am almost out already! I have a few left and as soon as those are gone I will order another batch. If anyone wants their own AT2XTKBD PCB please let me know!

Thanks and have a nice day!

Andrew Lynch
 
Great Hierophant said:
Thats it? I don't even see $5 worth of components there!

The interface on clickykeyboards is using a much larger chip, is the opposite conversion (XT to AT)more complex, hardware wise?
Click to expand...



No difference. A lot of people use whatever microcontroller they're most familiar with. The argument is that even powerful chips with loads of IO and peripherals are dirt cheap, but as cheap as it is I still feel like I'm wasting silicon so I use the smallest uC I can get away with. I'm fond of the Atmel AVR series myself, the ATTinys are available with 8 pins and dirt cheap.
 
I've just ordered the components for my batch of them. The total price is $9 plus shipping.
I can sell them in kit or assembled form, same price.
Caveat that I have not yet tried out my new PIC programmer to make sure I can do the programming, but aside from that, I should be ready to sell by the middle of next week. PM me.
 
Homemade one here (just modified for using a pic12f683 I had laying arround); works perfect but some of the localized keys (using spanish ps2 keyboard with keyb sp on msdos 6.22) are also in wrong place. It will be a good idea to track the changes and develop custom firmwares for some of the main localized keyboards out there.
I'll try with the spanish one, any advice?
 
You must log in or register to reply here.
Back
Top