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Thread: Help identify microcontroller in an XT keyboard

  1. #21

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    Quote Originally Posted by soon668 View Post
    Hi modem7, I should be able to purchase a Fujitsu FKB8720 keyboard locally. How do I go about building the AT2XT convertor?
    Just found the instructions here. Also I realised I can even use keyboard with PS/2 connector, which is much easier to find I also have the programmer already that I used to burn the Supersoft ROM I will try to build the converter and report back. After that I will try to troubleshoot the faulty XT motherboard that I had.

  2. #22
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    The converter can be constructed on a piece of perfboard--I did that for the original prototype. It could even be incorporated into the keyboard shell. If you use the TSOP version of the PIC, you could probably fit the whole thing into a standard DIN connector shell.

  3. #23
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    In case you did not see it, mentioned at [here] is the availability of prebuilt AT2XTKB (and some variants) on eBay.

  4. #24

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    I just build the AT2XT convertor on a perfboard, and here is the circuit diagram. I am using v0.94 of the firmware.

    However, during post, the AT keyboard LED light up once, and POST message "keyboard bad" appear, and ram count continue as normal. Typing anything on the keyboard does not have any effect. I have done most of the tracing to make sure the pins are all connected. I have also tried the jumper (ON/OFF) for the passthrough. The AT keyboard is new unused so it has not been tested either. Anything else I can check? Thanks.
    Last edited by soon668; January 24th, 2021 at 07:04 AM.

  5. #25
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    Have you verified the programming of the PIC? "Keyboard bad" error says that it's not responding.

  6. #26
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    Quote Originally Posted by soon668 View Post
    However, during post, the AT keyboard LED light up once, ...
    That is probably the keyboard doing a self test after receiving +5V.

  7. #27

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    Yes, I have verified the programming on the PIC using the programmer "Verify" function. I am also able to read back the content, although most of the content after address 3A0 are FF.

  8. #28
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    That's the way it should be--there's only 03FE worth of flash on the thing. Which PIC MCU did you use?

    Time, I think, to do some probing with a scope or a logic probe. The design's pretty mature.

  9. #29

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    I am using PIC12F629

  10. #30
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    Okay, with the firmware, that should work right out of the box. Got a logic probe or scope?

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