NWA-PCUG Newsletter Article, November 2002
USB To Whatever
by Fred Langa
From The LangaList Letter: USB-To-Whatever Oct. 7, 2002

Fred Langa illuminates the pervasive but little-understood world of USB, explaining how to hook it up to non-USB systems and peripherals--even in DOS!

USB stands for "Universal Serial Bus," and some newer PCs take the universal part very seriously: These machines may have no parallel (printer) port, no serial (comm) port, no keyboard port, no mouse port, no game (joystick) port, etc. Instead, the system typically will have two or four USB ports, and that's that.

Some PCs don't go quite that far, and instead offer a hybrid combination of ports. They may, for example, provide older PS/2- style (round) mouse or keyboard ports, but have no classic serial or parallel port, using USB for these functions instead.

Still other PCs (from just a few years ago) may lack USB ports altogether, instead providing only classic-style ports.

All these cases can lead to port mismatches: You may have no good way to connect a perfectly good printer, modem, mouse, keyboard, scanner, camera (or whatever) to your PC. The problem can be at either end of the connection: in going from a USB device to a non-USB port, or from a non-USB device to a USB port.

Even if you can make a physical connection between your external hardware and your PC, you may still run into software trouble. For example, if you ever use an older operating system (like DOS) on your newer PC, you may discover that none of your USB devices work: On its own, DOS doesn't know about USB devices, and has no intrinsic way of making them work.

Fortunately, there are work-arounds that can help you make working connections between USB and non-USB systems and peripherals, and even get USB devices working in DOS. With a little cleverness -- and maybe an adapter -- you probably can connect just about any piece of hardware to just about any PC, and make it work. Here's how:

Connecting A USB Device To A Non-USB PC
Sometimes, it's amazingly easy to connect a USB device to a non- USB PC--at least, when the USB device is a simple one such as a basic mouse, keyboard, joystick, and the like. In cases where the USB device isn't making use of USB's more-advanced capabilities and is simply transmitting exactly the same data as the non-USB version of the device, all you may need is the right physical plug to pass the signals through. Many vendors include these simple "pass-through adapters" in the box; and if one is available for your plug-in device, it's about the easiest way there is to overcome a port mismatch.

If your vendor didn't provide an adapter plug, you may be able to buy one for just a few dollars. For example, this Google search http://www.google.com/search?num=50&hl=en&lr=&ie=ISO-8859- 1&newwindow= 1&safe=off&q=%22ps%2F2+to+usb%22&btnG=Google+Search shows several merchants selling PS/2-to-USB mouse converters for under $9. Of course, keyboards and mice are inexpensive devices in themselves; it may make more sense simply to buy a replacement that has the plug type you need.

More complex USB devices (such as external USB hard drives, CDs, and the like) can't make use of a simple pass-through adapter; they must be plugged into a true USB socket. What do you do then?

The answer is an add-on USB host adapter card. These cards start at around $25 for the most basic models, and let you add two or four USB ports to PCs (and laptops) that originally shipped without USB hardware support. See this: http://www.google.com/search?q=USB+card or this: http://www.google.com/search?q=add+usb+ports for many inexpensive examples.

Either an adapter plug or add-in host controller will take care of the physical and electrical connections between a USB device and a non-USB PC, but what about the software?

USB Drivers (Even For DOS)
Windows XP, 2000, ME, and 98 all intrinsically support USB; and even ancient Windows 95b can be made to support USB if you download a supplemental patch. Alas, Microsoft says that USB supplement is no longer available, but many third-party sites still offer it. See, for example, this site or this search.

Third-party sites also are a gold mine of additional information not only for enabling or adding USB to Windows, but also for other operating systems. Just check the Web sites of any vendor who sells USB add-ons. For example, RamElectronics has an excellent how-to on adding or enabling USB in Windows, Apple, Linux, Be, and Unix at http://www.ramelectronics.net/html/usb- howto.html.

But what about DOS?
On its own, it knows nothing about USB devices. This can be a major hassle if, for example, you boot to DOS or start your PC from a DOS boot floppy, and then find that your USB keyboard and mouse no longer work -- your PC may start, but you'll have no way of controlling it! Or, even if the keyboard and mouse work fine in DOS, you still may lose access to USB peripherals such as an external drive or CD burner.

Although there's no single, universal fix for this range of USB/DOS problems, there are solutions to each piece of the problem.

For example, you may be able to enable DOS support for a USB keyboard through a "USB/Legacy" option available in some PC BIOSes. You usually can access your PC's BIOS set-up program by pressing DEL or some other specified key during the first few seconds of system startup. Once in the BIOS setup program, search the settings that relate to USB, and see if there's a "legacy" option available to you. If so, simply toggling that one option may allow you to use a USB keyboard from DOS.

If the option isn't offered or doesn't work, try visiting your keyboard manufacturer's home page to see if they offer a DOS driver for your specific brand and model of keyboard.

Alternatively, your PC's original manufacturer set-up CDs may also have DOS-level drivers, too; they're sometimes included with newer PCs to enable the use of a USB keyboard or mouse with the DOS-level "system restore" or "system recovery" software. You may find drivers in other odd places, too, once you start looking. For example, reader Karl Tipple found a DOS driver for his USB mouse that way:

    'Hi, Fred, I discovered that if you put the "hidusb.sys" file on your boot floppy and load it at the A: prompt in DOS, the USB mouse will then work in [DOS]. I figured this out when I tried to use a USB mouse in WIN98SE with [DOS-level] Drive Image and discovered that the PS2 mouse driver wouldn't work.'

Hidusb.sys is actually a Microsoft USB driver originally from Win98 but included in later Windows versions, too: Just search your system for the file, and it probably will be there.

Many other vendors offer similar files that are specific to a particular device: Be sure to check the Web site of the vendor whose USB device you're trying to get to work in DOS. As one random example, "PockeTec," a maker of external USB hard disks, offers DOS drivers for its product line.

If a targeted search doesn't work, you can try a more general one. You might start with the free pages at "USB-Drivers.Com" which list thousands of USB drivers and related files from hundreds of vendors. Or you can try a Google search using the name of your vendor or product, along with the words "USB DOS DRIVER" as search terms.

If that still doesn't turn up what you need, you may find success with any of several freeware, open-source, and shareware drivers that bring DOS support to a variety of USB devices. For example, the "DarkeHorse USB Resource" page lists DOS drivers for USB external CD drives, hard drives, and mice. The long "Interesting DOS programs" page also points to a variety of DOS/USB sites-- just search the page for "USB" to find 'em. New DOS/USB support pages are cropping up with some regularity, too, and a general Web search for "DOS USB DRIVER" may turn up just what you need.

Connecting A Non-USB Device To A USB PC
So far, we've looked at connecting USB devices to non-USB systems. But what about the other way around? What if you have, say, an older external modem that still works fine, but that needs a classic serial ("comm," or RS-232) port to plug into? If your new PC has only USB ports, do you have to toss the modem?

And what about older printers, scanners, cameras, or myriad other devices that connect through a classic serial or parallel port? If your PC only has USB ports, do you have to throw away this older, but still-functioning hardware? Maybe not.

Let's look at serial port devices first. Here, the answer is a special adapter with (1) a USB connector on one end and a classic RS-232 serial socket on the other; and (2) a tiny built-in microchip that converts data from USB format to RS-232/comm format and vice versa, allowing high-speed two-way communication through the adapter. To use the adapter, you have to load a device driver into Windows: Windows then sees the adapter as if it were a new ordinary comm port on your system.

Because Windows thinks it's simply acquired a new comm port, almost any serial device should work fine with this kind of adapter. For example, I wanted to connect my GPS (which uses an RS-232 serial port) to my laptop (which has only USB ports). A USB-to-RS-232 adapter worked so well that I bought another to use on my desktop system, so I could plug the GPS into the front- panel USB port, instead of having to crawl under the desk to get to the RS-232 serial port on the back on my PC.

There are literally dozens of such adapters available. Prices vary, but you can get a basic USB-to-RS-232 adapter for $20 to $30. See, for example:


Similarly, there are tons of USB-to-parallel (printer) port adapters that can help you connect printers, scanners, and the like to USB systems:


So, no matter what you're trying to connect, there's probably an adapter out there that will do the job. Seek, and ye shall find!

What USB sites, downloads, or tips have you found to be particularly useful? Join in the discussion!

To discuss this column with other readers, please visit Fred Langa's forum on the Listening Post.

To find out more about Fred Langa, please visit his page on the Listening Post.

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