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Thread: DirectIN PCB v2010 Keyboard - signal speed

  1. #1
    Join Date
    Jul 2011
    Posts
    2

    DirectIN PCB v2010 Keyboard - signal speed

    Hello,
    I have a question about DirectIN PCB v2010 Keyboard, and how the 1ms delay between a keypress and its registry by the CPU is achieved:
    Is this achieved through:

    1) Internal time-stamping of key presses within the keyboard (i.e. is there a built-in clock within the keyboard), OR

    2) Sending the signal triggered by a key press to the CPU in a millisecond? (in which case the speed with which keys press times are registered will depend on the speed of the USB port polling rate (i.e. once every ~8ms)).

    3) any other ways?

    Thank you,
    C

  2. #2
    Join Date
    Nov 2005
    Posts
    294
    Hi C,

    The keyboards don't use any internal time-stamping. Rather, the key position data is collected from each button within 1 mS, and the computer is instructed to poll the keyboard every 1 mS.

    John

  3. #3
    Join Date
    Jul 2011
    Posts
    2
    Hi Jon,
    Thank you for your response. Are there any adverse effects of changing the typical polling rate of the keyboard that I need to be aware of? I will be using the keyboard with a machine running windows xp, and microsoft engineers do not recommend overclocking the usb polling rate (Apologies of possibly unnecessary questions, I have no background in any sort of hardware/software/engineering).

    C

  4. #4
    Join Date
    Nov 2005
    Posts
    294
    The official USB spec clearly allows for interrupt transfers happening at a 1 mS rate.

    Our customers have used the keyboards and button boxes on Windows XP & 7 machines for many years, and we've never heard of any adverse effects on their other hardware.

    Connecting an oscilloscope to the USB bus will easily show that the transfers are in fact occurring at the specified rate. I'm not sure why the Microsoft engineers would specify otherwise.

  5. #5
    Join Date
    Dec 2011
    Posts
    1
    Hello,

    I have some concerns about the High Speed Keyboard. Isn't a driver necessary to get the USB port polling rate to 1ms ? Is there a way to check that it is indeed sampling accurately ? Moreover, is there something to specify in the program (Presentation scenario for example) for it to sample at this rate, or does it do it automatically ?

    Thank you, hope to hear from you soon.
    Svetlana P.

  6. #6
    Join Date
    Nov 2005
    Posts
    294
    Hi Svetlana,

    No, no extra drivers are required. Because of how the internal firmware of the keyboards and button boxes is written, the proper timing is assigned automatically.

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