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PC Keyboard rewiring

Discussion in 'Electronic Design' started by [email protected], Mar 30, 2006.

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  1. Guest

    I am having the following problem shown in this diagram, and have a
    solution that I think might work - but I am not sure.
    Here is the diagram:

    My problem is that I am trying to build a music controller -
    essentially a bunch of sample triggers - and this is most cheaply done
    via keymappings, which the software (Ableton Live 5) supports. But, to
    get the keys I need, I will use almost every key and its shifted

    This has led to two issues:

    One, I can make EITHER the shifted keys work OR the non-shifted keys,
    simply by activating the keyboard matrix's shift key and then wiring
    spst switches to the other mappings. Alternately, I can of course leave
    the shift key off, and wire stuff that way.

    Two: The other issue is if I attach the shift leads to two switches,
    each switch will turn on ALL keys hooked to the switch - enabled wires
    - I guess the current flows through the whole circuit, so I was
    thinking diodes might be the answer.

    I even though about using TWO usb keyboards, and wiring one for the
    shifted and one for the non-shifted keys. Either way, though, I cannot
    permanently wire the shift key in the ON position, and so I still must
    solve problem #2 in any case.

    I'm very new to electronics, though so this might be off base. I know
    there HAS to be a solution - because obviously, the keyboard has the
    ability to do this prior to dissassembly!

    If anyone can suggest another solution - like a way to send the keys
    from a custom-built controller that sends the ASCII codes, or the scan
    codes - I'd be interested in other options as well. One other
    potentioal snag with my plan is that if I press a button to a shifted
    character and another to a non-shifted char, BOTH chars will be
    shifted, unless I can somehow figure a way to send the signals

    If you want to see the controller concept I am building, you can see it
  2. Tim Wescott

    Tim Wescott Guest

    There are a number of projects that use PC keyboards, and the protocol
    to the computer is well documented. Do some web searches, see what you
    come up with.

    If it were me, even though I'm pretty good with this kind of stuff, I'd
    be tempted to find a project that replaces a keyboard and start with that.


    Tim Wescott
    Wescott Design Services

    Posting from Google? See
  3. I wouldn't say "well documented." Just prolifically. I haven't seen
    anything on the web either as accurate or as detailed as my copy of
    IBM's Technical Reference series on the subject of the traditional
    keyboard. Even taking multiple sites together. Which is too bad
    because that information is important for robust use and not easily
    inferred through examination.

  4. Guest

    The problem is that I am new enough to electronics that I might not
    understand what's been written! This is totally new territory for me,
    and what I have learned so far has been through experimentation only.

    I've certainly been searching for the info, but either I don't know
    what to search for or the info isn't documented. The closest I have
    found were people referring to "key ghosting", which gave me the diode
  5. Rich Grise

    Rich Grise Guest

    People have been doing this for decades - in fact, there are boxes on
    the market that accept a whole bunch of contact closures and send
    keycodes to the PS-2 keyboard port. I don't konw if they have them
    in USB yet. Here's a place to start:

    Have Fun!
  6. Rich Grise

    Rich Grise Guest

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