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Scanner or Printer Not Responding, or Stops Responding On USB Ports
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. ======== |
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