The USB interface has pretty much replaced the old serial ports that used to be part of every PC. Most laptop manufacturers got rid of serial ports a few years ago, and quite a few desktop machines no longer have them either. Unfortunately, most portable GPS units and NMEA 0183 adapters still require a serial port, so what's a boater to do? In this article, I'll try to provide a few answers to that question.
For installations where only a serial port laden GPS will be connected to the PC, the best solution is probably to use a "USB to Serial Adapter" (sometimes called a "USB to RS-232 Adapter"). Many of these devices are available with prices ranging from $20 to over $1,000. The lower-cost adapters are typically a one-to-six foot cable with a USB plug on one end and an oversized serial port on the other. Theoretically, these things should be very simple to use; just plug the USB end into a PC and plug the GPS into the other end and go. Unfortunately it's almost never that simple.
The problem is that many of these adapters were made available a five years ago when Windows 98 was the big thing and haven't really been updated since. Quite a few of the products will claim to work with Windows 2000 or Windows XP, but they don't tell you that you'll have to download and install new drivers until you reach customer support. Even then, many of the devices just don't work reliably.
Surprisingly, it seems to be the "big guys" that have the faulty products in this category. Belkin, well known for good cables and other things, has probably the worst adapters available when used with Windows XP. IOGEAR, ATEN, and Tripp-Lite all sell the same device with different drivers, but they all seem to have problems. On the other hand, Keyspan and Cables-To-Go have low-cost products that are reported to work quite well on Windows 2000 and Windows XP. We recommend shopping around and reading reviews before making a purchase.
Of course you could bypass the adapter and just get a USB GPS, right? Well... Unfortunately no standard exists for using a GPS over a USB connection. Most manufacturers include (or offer) drivers that attempt to emulate a normal serial port so that the USB GPS actually looks like a serial GPS to any software that uses it. Luckily these drives do tend to work better than the drivers included with USB Serial Adapters.
One popular USB GPS, the DeLorme Tripmate, does not include a virtual serial port by default, but if you can follow the many steps outlined on their website on this page: http://www.delorme.com/support/gps/uemate008.asp then you will be able to use that GPS with Coastal Explorer (or just about any other GPS enabled software).
If your setup includes a GPS that uses the NMEA 0183 (RS-422) electrical interface, or you also want to connect an autopilot, depth sounder, and/or other equipment, then a "USB NMEA 0183 Multiplexer" is the adapter for you. These adapters will let you connect up to four NMEA 0183 "talker" devices to your PC as well as let your PC talk to several NMEA 0183 "listener" devices.
These adapters are manufactured by a few companies, and we haven't heard any complaints about any of them. Here are the manufacturers we know of:
NoLand Engineering: http://coastalexplorer.net/Articles/www.nolandengineering.com
If you already have a Serial NMEA 0183 Mulitplexer, but your new computer only has USB ports, then you should be able to use a USB to Serial Converter to connect your multiplexer to your new PC which will be cheaper than replacing the multiplexer, but you may have a harder time figuring out what's broken if there is ever a problem.
I hope this information helps, at least a bit! If you have any real-life experiences using any of these devices that you'd like to share or have any other comments or questions about this article, please write me at firstname.lastname@example.org.