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Scanner or Printer Not Responding, or Stops Responding On USB Ports

Discussion in 'Hardware' started by Jerry Greenberg, Aug 4, 2004.

  1. This is a point of interest that I thought would be interesting to
    post.

    The described problem can be very frustrating, and sometimes very
    difficult to resolve. Many users would first start by uninstalling and
    reinstalling their software, when the software is not at fault.

    A very frustrating problem, especially with some USB scanners and
    printers is that the device may stop responding, or not properly
    respond.

    At the hardware level, and at the Windows test level, the device
    checks to be okay, and responding properly. Yet, it does not respond
    properly when doing its work.

    Some symptoms are that the scanner may stop in the middle of the scan
    and hang, or not scan at all. Or, a printer may stop in the middle of
    a page and hang. In the case of the printer, if it does not hang, it
    may start to print random looking characters during the middle of a
    print job.

    It turns out that with USB 2 ports, on many P4 machines this problem
    may occur with some scanners and printers. This has to do with several
    factors.

    If the USB Root Hub is IRQ shared with other devices that are
    particularly active, this problem may occur in many systems. This has
    to do with data streaming being interrupted (shared IRQ requests), and
    the receiving load becoming timed out. The device becomes out of sync.
    The device may then hang, or stop responding, and have to be reset.

    There is also the condition where the data inputs of the device being
    driven by the USB port are pulling peaks of too much peak current for
    the USB port. Considering the speed of the data coming from the port,
    the effective impedance of the device load may be a bit low, thus
    causing it to pull more current than what the USB port can support.

    This is a very basic overview of what the problem is with these
    situations.

    --

    An easy fix for this condition, if in the event that the condition
    described here is relevant to the problem described, is to add an
    externally powered USB hub between the USB port and the unit that is
    having the loss of the normal responding condition.

    The external powered USB hub will act as a data and power buffer
    between the device, and the computer's USB port. In this case it is
    effectively acting as an extended data port, with its own independent
    port power drive.

    Connecting and using other devices to the same hub, may or may not
    cause any symptoms of loss, depending on the particular
    characteristics of the other devices sharing this USB hub, and the hub
    itself. This would be by trial and error.


    Jerry G.
    ========
     
    Jerry Greenberg, Aug 4, 2004
    #1
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