Troubleshooting USB connections
Having problems with your USB connections?
This can be a tricky problem to troubleshoot because of the fact that each USB device requires different hardware settings, which can conflict with other USB devices. Since multiple USB devices share a single path into your computer, it can be confusing (and time consuming) trying to isolate the problem.You might be dealing with driver issues on a single USB device, compatibility issues between the devices plugged into the same USB slot on your computer, or even a problem with your USB cord or slot in your computer.
Before you start troubleshooting a USB problem, double-check the fundamentals: Does your USB cable have a good connection? Confirm that any USB hubs are properly connected and plugged in to powered electrical outlets. Many failures can be traced to unplugged equipment or devices that are plugged into outlets that are not receiving power.
To isolate the problem, have a simple USB device that works properly on another computer, such as a USB mouse. You can test this device on the computer experientcing the problems to verify that the USB port, not a faulty device or cord, is causing the problem. Here are some other common issues with USB connections and how to fix them:
- No USB device will work
Possible causes: Operating system compatibility, controller/hub compatibility, configurations for USB controllers, controller drivers
Make sure that your operating system supports USB, then check all of your devices to make sure they are supported by the controller. Next, check the controller’s settings and drivers. (Each of these things must be compatible with each other.)
- All devices occasionally stop working at the same time
Possible causes: Controller drivers, Power management, USB controller configurations, bandwidth
Bandwidth can be an issue if several devices are transferring large amounts of data. Common devices that hog bandwidth include printers, scanners, hard drives, cameras, and DVD/CD drives. To solve this, you might try dividing the USB devices between different USB root hubs.
If your system experiences sporadic controller failure, you probably have a problem with power management. You might have bus-powered scanners or hard drives that are drawing more power than your computer can provide. If your computer requires more power, try replacing your computer’s power supply with one that provides more watts.
- Several devices work fine, but others won’t work
Possible causes: Controller/hub compatibility, USB controller configurations, power management, controller drivers, device drivers, bandwidth
First move one of the working devices to another root hub to see if the problem is in a particular root hub or with the devices themselves. Next, remove external hubs from the equation to see if they are the problem. Try the problematic devices individually on the computer. If they work, it’s either a device driver or power issue. If they don’t work, it’s a controller compatibility issue, a device driver problem, or a lack of bandwidth. To solve compatibility issues and driver errors, try updating the drivers.
- Several devices occasionally stop working at the same time, while others are fine
Possible causes: Power management, device drivers, bandwidth
First, try to isolate the particular event that’s common to all failures. Your system might be experiencing a sporadic controller failure if your devices are split across root hubs. Try moving the devices to another root hub to see if the problem is in a particular root hub or the devices themselves. Remove external hubs from the equation to see if they are the problem. Try the problematic devices individually on the computer. If they work, it’s a device driver, power issue, or bandwidth pinch.
- One device never works
Possible causes: Device drivers, Controller/hub compatibility, Power management
If the device works on another computer, check to make sure it is compatible with your controller. If your device is bus powered and it never activates, lights up, or registers with your computer, then a power issue may be to blame. Next, check your drivers to see if they are compatible or need updated.
- One device occasionally stops working
Possible causes: Device drivers, power management, bandwidth.
Again, isolate the particular event that’s common to all failures. Move the device to another root hub to see if the problem is in a particular root hub or the device itself. Remove external hubs from the equation to confirm they are not the problem. Also, try using the device when no other USB peripherals are connected. You probably have a driver problem, but it could also be a problem with the power or bandwidth.
Solving USB Issues:
Operating system compatibility
Several operating systems don’t support USB:
- Some Windows 95 releases
- Windows NT
- Mac OS prior to 9
- Linux kernels prior to 2.2.7
If you’re using Windows 95, go to USB.org, check the FAQ, and download the USBReady.exe program, which will tell you if your Windows 95 computer is USB compatible. The new USB 2.0 standard may require additional drivers or patches that aren’t included with the OS. Check the device’s documentation for more information.
USB computers manufactured more than a year ago are limited to USB 1.1 devices. USB 2.0 is much faster and is usually backward compatible with the older 1.1, but it’s possible that a USB 2.0 device could refuse to work on a USB 1.1 controller or external hub, so check to see if there’s a compatibility issue.
Assuming a firmware update is available, you may need access to a USB 2.0-equipped computer to apply it. Check the manufacturer’s Web site for information on using your USB 2.0 device in a USB 1.1 system.
Configurations for add-on USB controllers
Check the Windows Device Manager to see if the USB controller is recognized or is experiencing a conflict.
- For Windows 2000:
Click Start, Programs, Control Panel, System. Then choose the Hardware tab, and then click the Device Manager button.
- ForWindows XP:
Click Start, Control Panel, select the Systems applet, click the Hardware tab, and then click the Device Manager button.
The Device Manager will likely refer to the USB controller as a USB Root Hub, USB Controller, or USB Bridge. The usual suspects of IRQ addresses and memory address conflicts are the first things to check. PCI devices shouldn’t have many problems, being Plug and Play, but EISA cards may require more adjustment.
If the hardware appears to work, reinstall the drivers. If that fails to resolve the problem, relocate the card to another slot in case a master/slave configuration error is occurring.
Integrated USB controller settings
If you suspect the trouble is with your USB controller settings, check the Device Manager for a conflict. Depending upon how well integrated the controller is with Windows, you may be able to adjust the IRQ or memory address settings from the Device Manager.
Next, try rebooting your computer and entering the BIOS configuration. USB settings are usually listed in the “peripherals” section. You’ll need to check for an entry marked “USB Controller” that is off or inactive. If this entry is already active, check the IRQ and memory addresses. Use the Device Manager to ensure that no other device is using those settings. You may need to reboot a few times to find a valid IRQ/memory address combination that won’t conflict with other devices.
If the hardware settings are fine, reinstall the drivers.
- USB keyboards
When editing the BIOS, enable “DOS USB Keyboard Support.” Enabling this option will allow you to use a USB keyboard when booting a system with a boot disk.
- Controller drivers
Check the motherboard manufacturer’s web site for driver updates. Many motherboard suppliers release driver combinations that include a number of hardware drivers. Confirm that you have the latest driver installed. Some operating systems also provide drivers, so make sure you have the latest available software patch as well.
Most computers have some form of sleep mode connected with the screensaver. A controller is not harmed when an energy setting kicks and eliminates its power. However, the OS may fail to power up the controller again. You can eliminate this error by opening Power Options and disabling System Standby.
In Windows 2000, access the Power Options applet by clicking Start, Settings, Control Panel, Power Options.
In Windows XP, go to Start, Control Panel, Power Options. You’ll find the System Standby option on the Power Schemes tab, which opens by default.
For laptop computers, you shouldn’t disable the power management permanently. If the manufacturer doesn’t have a patch for the laptop, consider switching to non-USB devices when possible. You could also create two profiles for users: a portable profile with power management enabled and a desktop profile with power management disabled.
Excessive loads on the bus can also cause power problems. The USB controller can power USB devices. Small devices like your mouse and keyboard aren’t a significant drain, but larger devices, such as scanners, hard drives, web cams, and speakers can draw considerable power. You might be able to eliminate the problem by spreading the power-hungry devices across multiple root hubs. Otherwise, acquire a good self-powered external USB hub.
Inexpensive external hubs sometimes fail to meet the USB power specifications and subsequently cause all devices on the hub to fail. Upgrading to a USB hub that supplies more power solves this kind of problem.
USB device drivers
The ability to hot-swap USB devices is a great feature, but it relies on a somewhat oversimplified set of all-purpose drivers. Some devices may appear to be general-purpose devices when in fact they are not. You need to install the drivers before you connect the device to the PC. Sometimes you need to reboot to give the new drivers priority over the all-purpose drivers. Skipping the reboot will break the whole process.
If you think the new drivers aren’t receiving priority, completely uninstall the device in question. You may have to leave the device connected to uninstall it properly. At other times you may be able to remove a device’s drivers using Control Panel’s Add/Remove Programs applet, just as you would with other software.
Sometimes it’s necessary to upgrade a device’s firmware, which is basically a driver that runs on the peripheral. The more advanced the device, the more likely it is that the firmware can be upgraded. Your mouse probably doesn’t have any firmware upgrades. Scanners, hard disks, printers, optical disks, and other sophisticated peripherals likely have upgradeable firmware. Check the manufacturer’s site to make sure that you have the most recent update.
USB root hubs can each support up to 128 devices, but they can run out of bandwidth, depending on consumption rates. USB 1.1 is limited to 12 Mbps, not counting the bus management overhead. USB 2.0 has 480 Mbps with about 420 Mbpsavailable, so it can support more devices. Combine an Ethernet adapter, a printer, and an external CD-ROM or hard drive on a single USB controller, though, and the PC can quickly exhaust its capacity.
The only solution for bandwidth problems is to either stop using all the devices simultaneously or distribute the load. Make sure you put devices that will always see use, like Ethernet adapters and USB speakers, on different root hubs. You may need to get additional USB controllers, which are inexpensive, typically costing less than $40.