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AT to XT Keyboard Converter

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    AT to XT Keyboard Converter

    I want to know if anyone has ever designed a converter box that will make an AT keyboard, like the most of the IBM Model Ms and other more modern 101 and 104 keyboards, work properly in a PC/XT that expect an 83-key keyboard or need a keyboard with an XT/AT switch. I have heard of boxes that will let an XT keyboard work in a modern system that expects an AT keyboard, but has the reverse been done?
    My Retro Computing and Vintage Gaming Blog : http://nerdlypleasures.blogspot.com/

    #2
    If it hasn't, drop me a line. I've probably got enough code to put something together in a uC.

    Comment


      #3
      wiki page is here with all the details distilled from this thread:
      http://wiki.vintage-computer.com/ind...oard_converter


      I too would be interested in such a device.
      I would like to use my PC/XT machines on a KVM switch with my 286+ machines.

      sounds like we may have another VC forum project on our hands! Go chuck go!
      Last edited by hargle; May 18, 2010, 06:12 PM.

      Comment


        #4
        There has certainly been a box to do the opposite, and they go for about $100 if you can find a custom one online.. Perhaps they work in either direction?
        More commonly known as "Yushatak" - www.yushatak.com
        Focused on 486 and Pentium Machines
        I collect All-In-One PCs and Keyboard PCs, especially Compaq.

        Comment


          #5
          I'll put this one on my to-do list, unless someone beats me to it.

          Comment


            #6
            If you feel like building custom ones for XT-to-AT I'd buy one.. Hopefully not at $100 tho :P
            More commonly known as "Yushatak" - www.yushatak.com
            Focused on 486 and Pentium Machines
            I collect All-In-One PCs and Keyboard PCs, especially Compaq.

            Comment


              #7
              i'd like one of these boxes too. i have one of my 8088s on a KVM switch but it's a pain because i have to keep a separate keyboard sitting on top of the tower and make room for it on my desk when i switch to it.

              making a converter would be pretty trivial with a very very low powered single board computer, 2 serial ports, and a little bit of ROM code.

              read the tech details of the XT keyboard protocol here:

              http://www.cs.cmu.edu/~jmcm/info/key2.txt



              tech details of the AT/PS2 protocol:

              http://www.beyondlogic.org/keyboard/keybrd.htm




              a possible cheap-o solution would be wiring an AT style keyboard into one of the 8088's serial ports and using a specially designed TSR to interpret and move the data into the computer's keyboard buffer, but i'm not sure if that would work for all software or not.
              Last edited by Mike Chambers; June 3, 2009, 06:23 PM.
              sigpic

              Comment


                #8
                Originally posted by Mike Chambers View Post
                making a converter would be pretty trivial with a very very low powered single board computer, 2 serial ports, and a little bit of ROM code.
                With a decent small uC, you probably don't even need the serial ports--just bit-bang it.

                And, in fact, most uC UARTS can't be used--while the keyboard sends a start bit, it sends the remainder of the data in clocked synchronous mode--and uses an 11-bit (start+8 data+parity+stop) format. Most UARTs can't handle 8bits+parity.

                I'm first going to see if it'll fit in a PIC 12F629. That'd be very slick. Otherwise, I can use an ATMega8.
                Last edited by Chuck(G); June 3, 2009, 08:24 PM.

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                  #9
                  Check this link

                  I will get one for me too.
                  http://www.clickykeyboards.com/index.cfm/fa/items.main/parentcat/11066/subcatid/0/id/176955


                  http://www.cs.cmu.edu/~jmcm/info/key2.txt

                  My apex 8088 xt take at keyboard if it is use full i will upload the BIOS.
                  Last edited by nesan; June 7, 2009, 08:09 AM.

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                    #10
                    I just assembled the prototype in an old "Monitor Miser" box. It's scarcely anything--an 8 pin 12F629, a capacitor and a couple of resistors. (The LED is for debugging).

                    Given the right components (i.e. SMT), one could probably fit it inside a 5-pin DIN connector shell.

                    I'll be working on the code this week--I've already constructed the translation tables.

                    All in all, this looks like it will be very easy.

                    Attached Files

                    Comment


                      #11
                      Originally posted by Chuck(G) View Post
                      I just assembled the prototype in an old "Monitor Miser" box. It's scarcely anything--an 8 pin 12F629, a capacitor and a couple of resistors. (The LED is for debugging).

                      Given the right components (i.e. SMT), one could probably fit it inside a 5-pin DIN connector shell.

                      I'll be working on the code this week--I've already constructed the translation tables.

                      All in all, this looks like it will be very easy.

                      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?
                      My Retro Computing and Vintage Gaming Blog : http://nerdlypleasures.blogspot.com/

                      Comment


                        #12
                        Originally posted by Chuck(G) View Post
                        I just assembled the prototype in an old "Monitor Miser" box. It's scarcely anything--an 8 pin 12F629, a capacitor and a couple of resistors. (The LED is for debugging).

                        Given the right components (i.e. SMT), one could probably fit it inside a 5-pin DIN connector shell.

                        I'll be working on the code this week--I've already constructed the translation tables.

                        All in all, this looks like it will be very easy.

                        I would suggest building it into a small box that accepts both 5 pin DIN and 6 pin mini-DIN female connectors with a 5 pin DIN male cable coming out the other end. This way you can use any type of AT keyboard and you won't need an adapter. I would also include a small fuse just in case the KVM (or whatever) sends some bad voltage down the line.

                        Do you have a schematic yet?

                        IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
                        IBM PCJr Model 48360 640kb RAM, NEC V20,, jrIDE Side Cart, 360kb Floppy drives running MS-DOS 5.00
                        Evergreen Am5x86-133 64Mb Ram, 8gb HDD, SB16 in a modified ATX case running IBM PC-DOS 7.10

                        Comment


                          #13
                          Just a quick update--the converter is currently operating with an IBM Model M keyboard on an XT. I've still got to write some code to manage the keyboard LEDs, but otherwise, I don't have any unresolved issues.

                          The prototype is largely unchanged, other than getting rid of the LED (it's no longer necessary) and a couple of very minor wiring changes.

                          I'm not interested in building these myself unless there's a substantial interest in them, but I'll post the code and construction details for those who are. For those without a PIC programmer, however, I'm willing to furnish pre-programmed PICs for a small bit above my cost of the chip itself.

                          The PIC 12F629 is exactly right for this project--it's probably the minimum (about $1 in quantities) that will do the job, yet there's plenty of code space left in case someone wants to do something interesting, such as use the 128-byte EEPROM for keyboard macros for F11 and F12, for example.

                          Comment


                            #14
                            Originally posted by Great Hierophant View Post
                            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?
                            Yup, that's it. If I'd wanted to wire it up inside of a keyboard, it wouldn't even be that. Just a dead-bug bit inside the case.

                            As far as complexity, it's a wash. Converting XT to AT keystrokes requires that the converter understand bi-directional AT protocol, but so does converting AT to XT.

                            I'd say that there's little difference. I was tempted to try a 6-pin PIC 10F series uC, but there's just not enough I/O on one of those.

                            Hobbyists like to use the 16F84 because it's got a fair number of I/O pins and there's a lot of existing code for it, so you see it in a lot of designs. But wasting real estate and resources bothers me.

                            Comment


                              #15
                              Originally posted by Chuck(G) View Post
                              The PIC 12F629 is exactly right for this project--it's probably the minimum (about $1 in quantities) that will do the job, yet there's plenty of code space left in case someone wants to do something interesting, such as use the 128-byte EEPROM for keyboard macros for F11 and F12, for example.
                              Would it technically be very difficult to allow XT or AT keyboards to work with a Tandy 1000/A/HD/SX/TX? I know Northgate's keyboard supported XT/AT/Tandy/AT&T/Amstrad and even some Amigas.
                              My Retro Computing and Vintage Gaming Blog : http://nerdlypleasures.blogspot.com/

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