I need Another Serial
Port!
By
Chuck Rexroad, AB1CR
With the modern era of Ham
Radio, most of us use PCs in some aspect of our hobby. We may operate PSK-31, MSK, packet, or
have our PC control our rig or rotator.
What most of us do is wonder why we always need more serial ports than we
actually have. For the last few
years the Universal Serial Bus (USB) has been on virtually every PC made
(desktop or notebook). I have
looked longingly at the USB to serial interfaces, but they simply cost more than
I was willing to pay. Thanks to the
ubiquitous Palm Pilot and other PDAs, there is now a simple, cost effective
solution for those who need another serial port.
The
USB PDA adapter from Keyspan connects to the USB port on the PC and provides one
DB-9 type connection. (see figure
1) The adapter costs about forty
dollars, which is more than an additional serial board, but with far fewer
headaches. There is no need to buy
a serial card, open the PC, or go through what is often a significant
configuration challenge.
Installation is simply “Plug and Play”, and there is no manual setting of
Com ports, IRQs, or any of the other fun things normally associated with adding
a serial port to your PC. In my
case this means that I can now operate PSK-31 while using my logging software to
control my rig and running WinAPRS.
Installation
As
with many consumer devices, the installation procedure is not well
explained. Do NOT start by hooking
up the hardware to your PC. This
can cause significant damage to your current configuration files. Also, do NOT start by dropping the CD
into the tray and letting it install itself. The manual, included on the CD ROM,
states that one should not install in this fashion, but there is no icon for
reading the manual until after the installation has been
completed.
The
best way to install the USB PDA Adapter is to put in the CD ROM in (do not
connect the PDA adapter yet), and when it asks if you want to install, just say
no. Then go to Start, Run, Browse,
D (or whichever drive is your CD) and run the setup program. (This is the Keyspan’s recommended setup
process, although it is somewhat unusual.)
Once this is complete you will need to reboot your PC. Only after the reboot is completed
should you plug the USB PDA adapter in.
Windows will load the proper drivers and configuration, and you are ready
to use your new serial port! The
only question now is, what’s it called?
Go
to Start, Settings, Control Panel, System, then click on the device manager
tab. Now expand the section on
Ports (Com and LPT). You will see a
window that looks like figure 2.
You should see a new port called Keyspan Com Port (COM x). Where x is the Com port number that
Windows has assigned the new com port.
Simply configure your software to use this COM port, hook up the
appropriate device to the new serial port, and you’re good to go! Note, if your software does not allow
using the newly assigned COM port you may want to think about using the new COM
port for a different function and using your original hardware/software on one
of the original COM ports. In my
case, I originally planned on doing DX Cluster through the new adapter, but the
DOS version of Log-EQF (or any DOS based program for that matter) could not use
the new com port. Digipan didn’t
mind the new COM port a bit, so I moved my Rig Blaster to the new COM port and I
had accomplished my goal!
I
have done compatibility testing with the USB PDA adapter with a number of
programs and devices. Most Windows
based software will allow hooking up to the USB adapter if it will work under
Windows with your original serial ports and the software will recognize the Com
Port of the USB PDA adapter.
The
Keyspan USB PDA adapter works with Windows 98 and higher, and also supports
Mac. I have not done any testing
with the Mac environment. I have
seen discussions of Linux support in some of the Linux newsgroups, but as yet I
have not seen anyone provide this support.
There may be situations
where you need to set the properties of the USB PDA Adapter within the Windows
control panel. Most software
packages will override these default settings, but in my testing I did have to
set the defaults for at least one combination of
equipment.
To
set the defaults in Windows Control Panel, follow the steps above to get the
screen in figure 2. Single click on
the Keyspan COM Port and then click
on the properties tab. Select the
Port Settings tab and then set the following parameters: Speed = 4800, Data bits = 8, parity = none, stop bits =1, and flow control =
none, or whatever may be appropriate for your application. (NOTE: These values will work for most packet
and GPS configurations.)
The
Keyspan USB PDA adapter is available from a wide variety of sources. Shop around for the best price. Keyspan also makes a 2-port version of
this adapter, but that was not tested for this article. For those with serious com port needs,
there are also four-port USB to serial adapters, but they require a much bigger
checkbook!
One
final thought. The USB PDA adapter
is meant to be connected and disconnected at will. This means that if you also have
notebook PC that you want to use for APRS mobile, you may well be able to use
the USB PDA adapter in the car and have two serial ports on your PC. One will connect to the TNC and the
other to the GPS. As you can see,
the possibilities are endless!