|
||
 |
||
|
| Get USB To Work On Your PC |
 Email This
 Print ThisView My Personal Library |
|
Hardware November 2000 • Vol.6 Issue 11 Page(s) 48-49 in print issue |
Get USB To Work On Your PC | ||
 You're at home after having just purchased the latest racing car video game along with a driving console and an external drive to play the disc. You even bought a top-of-the-line subwoofer to hear the roar of the engine. You plug everything into the USB (Universal Serial Bus) ports on the back of the computer and sit down, ready to win your first race, and it crashes. No, not the car, your computer. So how do you avoid troubles with USB devices, and how do you fix problems if they occur? Fortunately, USB has a big advantage over older systems with its reliably connecting peripheral devices. Although problems occur, they are not as common these days and can usually be easily fixed.  What Is USB? Before we get into troubleshooting USB problems, a general understanding of USB and its properties will help you avoid many of the usual pitfalls. Basic PC architecture limits the number of internal and external devices that can be connected to your computer. It is not a question of merely adding more cards; it is a matter of how many of those additional cards the computer can recognize. But things have changed significantly since the 1980s when systems consisted of a processor, two 5.25-inch diskette drives, a keyboard, and a printer. Modems, mice, joysticks, CDs, DVDs (digital versatile discs), hard drives, sound cards, scanners, digital cameras, video accelerators, Zip drives, docks for PDAs (personal digital assistants) and laptops, speakers and microphones, and tape backup drives have been added to the mix. Some fundamental changes were needed, therefore, to accommodate these devices. In response, a system was developed that lets multiple devices use a single computer address, known as an IRQ (interrupt request line). In 1995, the original specification for USB was released. The new standard had several advantages. First, it allowed for as many as 127 devices to be connected to a single port on the computer. Second, with a 12Mbps (megabits per second) data transfer rate, it was 10 to 40 times as fast as regular serial or parallel connections. USB also offered easier set up because devices could be added or removed from the system while the system was running. Although this USB standard was released five years ago, it took several years before the software and peripheral devices to support it became widely available. The initial release of Windows 95, for instance, didn't support USB. The second release, Win95 OS/2, while it did include support for USB, did not load automatically as part of the system setup and contained various bugs. Plus there were few devices available that could take advantage of USB. This all changed in 1998, however, with the release of Windows 98. Most computer manufacturers began including USB ports in their machines and devices. USB has four parts: the controller, one or more hubs, the devices themselves, and the cables that connect them. The controller, which identifies and manages the devices on the USB, is contained inside the PC. It includes the USB device drivers (pieces of software tailored specifically for particular devices that lets Windows control or "drive" the devices). The main, or root, hub is also located in the computer with additional hubs connected to and controlled by the root hub in a master /slave relationship. Potential Problems. Theoretically, all you have to do to is plug in a USB device. The computer instantly recognizes it and loads the device driver. While it does work this way in most instances, there are a number of problems that can develop. We're going to take a look at a few of them and walk you through solutions when possible.
What can I do about an outdated operating system? If you are trying to get USB to work on an older machine, you'll probably encounter some difficulties. For best results, upgrade to Win98 SE, which has very few problems supporting USB devices. My hardware devices are malfunctioning or are incorrectly configured. When a malfunctioning or incorrectly configured device is plugged in, it generally causes the computer to stop responding. In these cases, you will have to physically turn off the computer to reset the bus. To verify which device is causing the problem, unplug and reconnect the device to see if the problems occur again. If the device is connected to an external hub, try plugging it directly into the computer instead. If you have another computer that you know to be working, plug the device into it to see if the problem occurs. Once you've isolated the offending device, follow the service instructions for that piece of equipment. You might also try visiting the device manufacturer's Web site to see if there are newer drivers available. If there are, download them, plug in the device again, and see if that solves the problem. Bandwidth shortage. A single USB port can handle only a certain amount of bandwidth, which it allocates between all of the active devices. A device that is hogging a lot of the bandwidth, however, can slow down or crash the bus. USB, therefore, is not designed for high data transfer items such as hard drives, DVDs, or video cameras. In such a case, move the item that needs the most bandwidth to its own USB port or get a high-speed port installed on your computer to accommodate the device. An alternative is to buy a USB switch and plug it in. This switch lets you select which USB devices are connected to the system. Power too high or too low. USB is a powered bus system designed to operate between 50 and 500mA (milliamps). If the draw on the bus is less than 50mA, it won't even read the device. If a device tries to draw more than 500mA, the system suspends or disables that port until you turn your computer off and on again. To find out how much power is being used on a bus, go to the USB Root Hub properties in the Device Manager and click the Power tab. To get there, click the Start button, select Settings, and then click Control Panel. Next, double-click the System icon and then click the Device Manager tab on the System Properties dialog box. Click the plus sign (+) next to Universal Serial Bus Controllers and double-click USB Root Hub. In the USB Root Hub Properties dialog box, click the Power tab and then the Power Properties button. In the Power dialog box, you can see what device is drawing too much power. You can then get a powered hub or a separate power supply for that device. Missing or malfunctioning device driver. Normally, the computer will load the driver for a new device on its own. If it prompts you for one, go ahead and load it. A safe operating rule is to assume that any device driver that you get when you buy a device is out of date. Check the manufacturer's website for the newest version before you install the device. Low-speed cables. There are two types of USB cables: high speed (12Mbps) and low speed (1.5Mbps). Both use the same kind of connector, but the high-speed cable has better shielding. If you use a low-speed cable to connect a high-speed device, it can result in signal distortion over long distances. Nonpowered hubs. There are also two types of external hubs: powered and nonpowered. A powered hub has a power supply that lets you plug it into the wall. It provides the full 500mA to each of its ports. A nonpowered hub depends on the root hub in the computer for its power. If a device that requires power from the USB cable is connected to the chain downstream from a nonpowered hub, however, it will cause that hub and all of the devices down the chain to be suspended. You can solve this problem by plugging the device into a powered hub. Duplicate devices. Normally when you remove and reconnect a USB device, the system automatically recognizes it. Sometimes, particularly with printers and modems, when you plug the device in again, it will reload the driver and duplicate devices will show up in the Device Manager. To fix it, download the latest version of the device driver from the manufacturer's World Wide Web site and install it. Delete the other device drivers for that item. Extension cables. Never use extension cables to exceed the USB limit of 5m (meters) for high speed or 3m for low speed. Exceeding the recommended distance will cause signal loss, and the devices may not install on the system. If you need a longer connection, use a series of cables connected by powered hubs to reach up to 25m. Connecting two personal computers. Normal USB cables have different sized ends. The A end plugs into the root hub on the computer, and the B end plugs into the device or another hub. There are also cables available that have A connectors at both ends. Although they look like they would be used to connect two PCs, never do that. When using one of these cables you are connecting the power supplies of the two computers together, possibly destroying both machines and creating a fire hazard. Instead use a device called a USB bridge to do the job. For More Information. The above advice will handle most of the problems you may encounter with USB ports or devices. There are, however, problems that can creep up with specific pieces of computer equipment. Online support is available for most of them. Start by checking the manufacturer's World Wide Web site to see what solutions the company has posted. The Microsoft support Web site at http://support.microsoft.com also has extensive data on both generic and device -specific troubleshooting. If neither of these have the answer you need, go to the USB support bulletin board at the USB Web site (http://www.usb.org) and post your problem there.  by Drew Robb
|
|
Home Copyright & Legal Information Privacy Policy Site Map Contact Us