IT Life

Langa Letter: USB-To-Whatever

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!
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!

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