lkml.org 
[lkml]   [1997]   [Aug]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Keyboard error
    On 11 Aug 1997, Linus Torvalds wrote:

    [...SNIP...]
    >The keyboard signals the error, and there is nothing the driver can do
    >about it. So yes, the answer is "don't do that, then".
    >
    >The deeper reason for the error can be found in how the keyboard
    >physcially scans which keys are pressed. For reasons of economy, most
    >keyboards have a simple "scanning array" where a keypress shorts one
    >array corner (*). Depending on how the array is set up, pressing
    >multiple keys will not always work - and the exact keys that result in
    >breakage depend on the topology of the scanning array.
    >
    >Many multi-key-presses will create a "shadow key press" (so when you
    >press three keys, the keyboard controller will actually think that
    >you're pressing four keys, and I suspect that the keyboard controller
    >just notices that two keys changed simulataneously and will consider
    >this an error.
    >
    >The keyboard array is usually set up in such a way that the "normal"
    >keys that are often pressed together (alt, shift, cursor keys etc)
    >create as few of these shadows as possible, but you've obviously found
    >one of them. I suspect that you'll easily find more by just pressing
    >lots of keys at the same time..
    [...SNIP...]
    >
    > Linus
    >

    Linus is on the right track here, basically some more expensive keyboards
    can take upto 7 keypresses (or more) at once, I found this out on a
    friends keyboard, two players on one computer/keyboard setup, and
    generally on cheap keboards you can get away 3 keypresses before you get a
    keyboard "lock", does anybody remember how DOS/BIOS complains:
    <bleep><bleep><bleep><bleep>....

    My keyboard does 6 keys bofore it stops sending anything (no errors,
    about AUS$100)

    ---------------------------------------
    "When all of your wishes are granted,
    many of your dreams will be destroyed",
    Man That You Fear - Marilyn Manson

    mabs@netdig.com.au
    ---------------------------------------


    \
     
     \ /
      Last update: 2005-03-22 13:40    [W:0.029 / U:31.332 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site