AT to XT Keyboard Converter

Keyboard Converter

Keyboard Converter

I got an ASCII converter from jasystems.co.uk they might be able to help you with the XT to AT converter. They definitely do the AT to XT converter.

wow, guys, I'm so out of this open source/non-profit business model.

jasystems.co.uk sells their AT to XT keyboard converter for *only* £75.00! That could be ~$110 pure profit for each controller that we're selling.
They do have theirs in a nice box though.

Honestly - you guys surprise me by selling this stuff at cost, even though it is for a hobby that you love. Many of the Amiga guys sell theirs for-profit, and it's the home-brew guys that are essentially keeping that hardware scene alive.

That said... I'm not complaining that I got my XT-IDEs relatively cheap, and it was fun to build it (still have one PCB) - even though I'm having trouble getting it to work in my PS/2 Model 30 and need to pull out my 5160 to attempt flashing before hanging it up and asking for expert help for the newbie solderer (i.e. me!)

Hi Guys,

I got the AT2XTKBD circuit board some time back in the hopes of converting my XT Keyboard for use with my PC visa PS/2. I had understood that of course the code for the PIC needed to be changed as i had planned to use it the opposite of what it was intended for.

After looking at the code i realized that a whole LOT more needs changing besides the translation lookup table for the scan codes. Like for example the functions processing the signals from the host were all done assuming that the host was an XT computer, and the functions processing the input from the keyboard were assuming that from a AT Keyboard.

From looking at the AT2XTKBD.sch diagram, my idea was to hook up the PC to the current "PS/2_Keyboard" port and the XT keyboard to the "XT_HOST" port. And re code the code for the adapter. Is this feasible (hardware wise)?

Next thing i can't figure out is what is the purpose of Jumper 1?

I think before i attempt this i need to understand more on how a AT host, and a XT keyboard behaves. Can someone please point me to some documentation on these? I seem to easily find docs for AT keyboard but not much is found for XT Keyboard.

Thanks!

J1 is used to tell the firmware to pass or filter E0 codes from the keyboard. Some non-US keyboards and BIOSes use these for added keys, while US-based BIOSes will choke horribly on them. No other solution than to use a jumper. I'd originally thought to use it as a jumper to determine the direction of translation (AT to XT, or XT to AT) if used with a PIC with a bit more program memory (they exist). On the other hand, it should be pretty simple to sample both ports and determine the translation direction automatically.

It's been awhile since I posted the source to this thing, so I"ll remedy that right now. Please see the commentary at the front of the source for specifics on operation.

Hi Chuck,

Thanks! for the updated code.

Hi! I still have a stack of the AT2XTKBD converter PCBs. They work great and are really inexpensive. Please contact me if you would like one or more. These are so handy its worth stocking up on them in case you want to use multiple computers. I think they can be modified to do the opposite conversion (XT2ATKBD) if you want too although I don't think the code has been published AFAIK.

Thanks and have a nice day!

Andrew Lynch

One cool aspect of the converter is that you can unplug the keyboard while the system is booted and then plug it in again without disrupting things. Good if you want to use a KVM that understands only PS/2-interface keyboards.

Hi! I've gotten some requests for the AT2XTKBD PCBs recently. There are plenty of them remaining so if anyone would like one or more please contact me. They are $5 each with $1 shipping in the US and $2 elsewhere. Please send a PayPal to LYNCHAJ@YAHOO.COM and I will send your PCBs right away!

Thanks and have a nice day!

Andrew Lynch

Hi

Where can i get that convertor?

Is it get with that programming chip on it, because some people doesnt have a programmer..

Hi, there are still plenty of the PCBs available. They are $5 each plus $1 shipping in the US or $3 elsewhere.

Please send a PayPal to LYNCHAJ@YAHOO.COM and I will send your PCB right away.

Thanks and have a nice day!

Andrew Lynch

Okay but there arent cases to store that pcb in?

Is it included with manual?

Welcome to these forums.

Be aware that what Andrew has is just the PCB (printed circuit board) only. You would need to go out and buy everything else, and assemble it yourself. That activity would include buying components, soldering, and programming the PIC chip using an EPROM programmer.

I think that a few members may have obtained the components and done the soldering themselves, but because they lacked a suitable EPROM programmer, sourced the programmed PIC chip from other members.

Member Hargle was at some time offering kits of parts (you do the soldering). I don't know whether or not he still does.

Robin4 said:

Okay but there arent cases to store that pcb in?

Click to expand...

A case is not required, and not supplied with the PCB. If a case is desired, you can always purchase one from an electronics store.

One implementation of using a case is shown at http://www.minuszerodegrees.net/misc/at2xtkyb_in_jiffy.jpg

Robin4 said:

Is it included with manual?

Click to expand...

No.

A schematic and parts list is at http://www.vintage-computer.com/vcforum/showwiki.php?title=AT2XT+keyboard+converter
That's intended for people who will know how to assemble/build the unit from such information.

It sounds to me like you are seeking an assembled unit (with or without case). Is that the case?

Also, which country/city are you in?

I sell completed units, in kit or assembled form, for $10 plus shipping. send me a PM. I think I have 5 kits left.
They do not come with cases or manuals. Something this simple really doesn't need a manual.
You will also need some kind of 5 pin cable to go between your PC/XT and the converter. MIDI cables work great, and are often about $5 or less for a 3 footer.

Hi! There are still several of the AT2XTKBD PCBs left. They are $5 each plus $1 shipping in the US and $3 elsewhere.

http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=MINI AT2XTKBD

Please contact me if you would like one or more of these PCBs. Thanks and have a nice day!

Andrew Lynch

Wasn't sure whether to put this in a new thread or not. Oh well, I will just stick it in here.

Just to let you all know, at least some USB keyboards will work with this converter! Not all. I tried my Unicomp Endura pro USB keyboard, which has a built in trackpoint-style mouse device. It did not work. This would make sense, as a mouse/keyboard combination probably wouldn't convert properly through a passive USB to PS/2 adapter anyway. I assume it could be the same on keyboards with extra USB ports on them, but I don't know.

Now, today I got a new keyboard (entry level mechanical with Cherry Brown switches - the iOne XArmor U9, USB interface) and decided to try, using the AT to XT converter, to connect it to my Leading Edge Model D. I used one of the simple purple PS/2 to USB keyboard converters and connected it to the AT2XTKBD, which in turn (obviously) is connected to the computer. To my surprise, the LEDs blinked and the keyboard worked (almost) fine!

I did notice that, when typing fast, it tends to skip, delay, or mistype characters sometimes. Mostly it just leaves some out. It could seem almost as if the keyboard itself has a buffer or a timing feature that is not quite in sync with the old 4.77mhz CPU. But the problem is worse when Caps, Scroll, and Number locks are on. Specifically when the LEDs are lit (since, on the Leading Edge, a lit LED is not always an accurate indicator of the lock status). So I thought it could be a power supply issue as well. The problem is almost nonexistent when no LEDs are lit. Odd.

Nevertheless, I would consider this a victory, as the keyboard is still usable. Curious to know if anyone else has tried adapting USB keyboards as well.

Hi! There are still some (about 9) AT2XTKBD PCBs left in case anyone else would like some. They are $5 each plus $1 shipping in the US and $3 elsewhere. Please contact me if interested!

Thanks and have a nice day!

Andrew Lynch

Chuck(G) said:

It's been awhile since I posted the source to this thing, so I"ll remedy that right now.

Click to expand...

Thank you very much! Is it possible to add the BIN file as well? I have an universal programmer that is capable of programming all kind of stuff including PIC. But I don't have a PIC assembler (yet).
Or can you recommend a PIC assembler (the one you use)?

Many thanks in advance!


Groetjes, Ruud Baltissen
www.Baltissen.org

I used gpasm. I believe that the chip-specific .inc file came from the MPASM include files from Microchip. I believe that gpasm produces a .HEX not a .BIN file. Most programmers should be able to accept that format, as it's been standard since the early 1970s.

Mine isn't as elegant. Almost 2 years ago in July, I threw together this DIN to PS/2 keyboard adapter because I wanted to go old skool with one of my old keyboards, plugged into my computer's PS/2 port. They use the same protocol. The only difference is in the pin layout. I looked for the original picture that was much higher in resolution, but I wasn't able to find it. I was only able to find this one. Hopefully you can discern the wire connections.

http://www.flickr.com/photos/9114793@N03/7488293002/in/set-72157630389996430/

Hope this helps you