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USB
Troubleshooting
This article describes general troubleshooting tips for Universal
Serial Bus (USB) devices in Windows 98, Windows 98 Second Edition, and
Windows Millennium Edition (Me).
MORE INFORMATION
Because USB devices are Plug and Play devices, there is little that you
can do to control or configure them. However, most you can trace most
USB problems to one of the following conditions:
- Malfunctioning or incorrectly configured hardware
- Malfunctioning, incorrectly configured, or missing device driver
- Mismatched cabling
- Out-of-date firmware or basic input/output system (BIOS)
- Improperly configured root hub
You can use the following troubleshooting tips to check for each of
these conditions to help you resolve USB device issues.
Malfunctioning or Incorrectly
Configured Hardware
Typically, if you plug a malfunctioning or incorrectly-configured device
into a USB port, it causes the computer to stop responding (hang). In
the majority of these instances, you must physically turn off the
computer and turn it back on to reset the bus. Note that it may be more
difficult to identify which device is malfunctioning or is incorrectly
configured. If another computer that you know is working correctly is
available, try to plug the device into that computer to see if you
encounter the same issue.
If the device is plugged into a secondary hub, unplug the device from
the hub and then plug the device directly into the root hub.
Many hardware problems (such as high or low power, bandwidth shortage,
malfunctioning or incorrectly configured firmware, and so on) can cause
issues to occur.
Check Device Manager to be certain that the root hub is functioning
correctly. If the root hub is displayed with an exclamation point in a
yellow circle, verify that the BIOS is assigning an interrupt request (IRQ)
to the root USB controller. This is required for the device driver to be
loaded. For additional information about how to use Device Manager to
troubleshoot hardware issues, click the article number below to view the
article in the Microsoft Knowledge Base:
133240
Troubleshooting Device Conflicts with Device Manager
If no devices work when you plug the devices into the root hub, verify
that the power requirements of the bus are not being exceeded. USB
devices can draw a maximum of 500 milliamps for each connection. If a
device attempts to draw more power than this, the specification
recommends that the computer be able to disable that specific port until
the computer power is cycled (this is called "suspending" the
port). In addition, if the device draws less than 50 milliamps, the port
never becomes active.
Check the Power tab in USB Root Hub properties to check
the power usage of the USB bus.
Malfunctioning, Incorrectly
Configured, or Missing Device Driver
When you plug in a USB device, the computer should load and then
configure the device without ever requesting a device driver (assuming
that the device falls within the defined and supplied class drivers). If
the computer prompts you for a device driver, check with the
manufacturer of the device to determine if a driver is available.
Mismatched Cabling
There are two types of USB cables, high speed and low speed. Low-speed
cables differ from high-speed cables primarily in their shielding. If
you plug a high-speed device into a low-speed cable, you can cause
signal distortion over long distances.
Verify the entire USB chain is working correctly to be certain that a
device that requires the ability to draw power from the hub is not
plugged into the chain on the other side of a non-powered hub. This
causes that hub and all of the devices down the chain to be suspended.
If the hub is a powered hub, verify that the power supply for that hub
is configured properly.
Out-of-Date Firmware or BIOS
The key to all USB devices is the firmware. The USB device's firmware
contains all of the information about the device. A port is not reset
until all of the descriptors in the firmware have been loaded and
verified by the root hub. This is critical because it applies to items
such as printers and modems. Make certain that you have the most
up-to-date firmware that is available for both your computer's BIOS and
each individual device.
The symptoms of malfunctioning or incorrectly configured firmware might
be unusual. Typically, when you remove and then re-add a USB device, the
device simply becomes available again. However, the device may appear as
a second instance of that device, and load itself as such in Device
Manager. If you see duplicates of a device, verify that you have the
most up-to-date firmware for that device. This issue is common with USB
printers and modems. A similar issue that has the same cause occurs when
a device loads a device driver and then adds a second device for which
there appears to be no driver. The second device is displayed with an
exclamation point in a yellow circle in Device Manager. The device may
work correctly, but you cannot remove the "ghost" device until
you unplug the parent device that seems to have generated the ghost
device. Also, you may be able to resolve this issue by updating the
firmware or the device driver for that device.
Incorrectly Configured Root Hub
USB controllers require that an IRQ be assigned. The IRQ line is
assigned in the computer's BIOS, and usually IRQ 9 is assigned
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