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Thread: Keyboard for Processor Technology board set?

  1. #1
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    Default Keyboard for Processor Technology board set?

    I have a PT board set for my IMSAI, however Iím missing a keyboard. Itís my understanding that a parallel keyboard can be used. The prior owner of my set appeared to use a parallel keyboard with the video board.

    Does anyone know where I can obtain an old mechanical keyboard that is compatible?

    Thanks

  2. #2
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    I'm working on an open source parallel keyboard that will work:

    https://github.com/osiweb/unified_retro_keyboard

    The keyboard is currently in beta testing, but is pretty solid. Keycaps are on order and still perhaps a couple of months out. There is a "classic" ASCII set and a SOL-20 supplement, if you want a SOL-20 keyboard to go with your PT kit.

    Dave

  3. #3
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    Hi Dave, I reviewed some of your source which you have targeted for the ATMega. What hardware components are required for your parallel prototype including keyboard itself? I am considering either your solution or searching for another older ASCII keyboard on eBay (which can get expensive). I’m still u sure which is the most economical approach. For SOL owners the capacitive keyboard are problem prone with the foam and a replacement set is about $40. Thanks

  4. #4
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    • The PCBs for the whole project (either SOL or classic style) are about $20/set in quantities of 5 from china, so a group buy helps.
    • The parts for the interface are perhaps $10, depending on what you have on hand.
    • The keys could be as little as $20 if you go with the futaba keys, although Cherry MX clones can be had inexpensively as well.
    • If you want the classic-style ASCII layout, the keycap set is about $60. If you want the additional Sol-20 keycaps, then that's another $60 (Keycaps are pricey, and the Sol-20 extension set has bigger keys, some with LED window).


    So, you're looking at something on the order of $110 for a new classic ADM-style keyboard, $170 for a Sol-20 keyboard replica. But that could be more or less, depending on your switch preferences, and what you have on hand.

    However, the keycaps are on order and are probably on hold until the state of Washington is out of lockdown, which could be a few months for all we know.

    If you are happy with a Selectric-style layout (1-!, 2-@, 3-#, ...instead of 1-!, 2-", 3'#, ...), then you could get very close with a set of PC-104 keyboard keys (double-shot molded ABS SA profile keys can be found for about $25/set). You would need 1.5u SHIFT and RETURN keys; you could use blanks though. That would cut the overall cost down to about $80. Less if you already have keys or keycaps, and much less if you have both keys and keycaps on hand.

    The source is not really targeted for the Atmega chips. The bulk of the code is portable ANSI C99, and the Atmega-specific code consists of a few functions in an architecture-specific file. It would be trivial to port to a PIC or an ARM chip. Picking a chip with more I/O would save a few bucks by not requiring any additional ICs.

    I have sent off gerbers for the latest revisions, so I will have 5 board sets available in a week, if you're interested.

    Dave

  5. #5
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    Quote Originally Posted by atod View Post
    Hi Dave, I reviewed some of your source which you have targeted for the ATMega. What hardware components are required for your parallel prototype including keyboard itself? I am considering either your solution or searching for another older ASCII keyboard on eBay (which can get expensive). I’m still u sure which is the most economical approach. For SOL owners the capacitive keyboard are problem prone with the foam and a replacement set is about $40. Thanks
    I guess I don't have a BOM in there. I will be working on putting up some documentation soon. I've tried to keep the parts list hobbyist-friendly. Parts include an Atmega328P chip (not my go-to chip, but chosen because it's familiar to many hobbyists); a couple of 74LS138 decoders, a 741LS66 shift register, and a 74LS04 inverter, plus some discrete parts and a DIP switch. All those extra TTL chips are needed only because the tiny atmega328p processor doesn't have enough I/O to drive all the lines directly.

    I periodically check Ebay for keyboards, and the prices seem to be moving upward. I think that keyboards can be had for less then $100, but harder to find. Another advantage of building your own, besides the flexibility, is that you can have it right away.

    Dave

  6. #6
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    Thanks. I’m considering it. I have also considered an Apple II keyboard as I understand they are ASCII encoded. These are pricey as well! It would also lack the numerical keypad section that the SOL keyboard has.

  7. #7
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    BTW, the "classic" layout can be configured as an exact Apple II replacement. The keycap set on order will include correct Apple II caps, including a translucent illuminated "POWER" cap (All CAPS version; if you select the Upper/Lower keymap via the DIP switch, then the "Power" button becomes a CAPSLOCK, with the light indicating the capslock status (initially active). The behavior is actually specified in the keymap.

  8. #8
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    Quote Originally Posted by dfnr2 View Post
    However, the keycaps are on order and are probably on hold until the state of Washington is out of lockdown, which could be a few months for all we know.
    I just found out that the keycap manufacturer is still operating, although at half capacity, and it looks like the keycaps might even be ready sometime in May.

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