COM ports

[Guest]

I have a USB to serial cable that I use on my laptop, but everytime I plug it
into my laptop, XP assigns it a new COM port number. When that happens, I
have to go thru the settings of my applications that use the COM port and
change them accordingly so that they communicate thru the adapter cable
properly. Is there any way that I can set XP to assign the same COM port
number to my cable everytime I plug it in? Thanks!

Jeff

 

[R. McCarty]

Several things may help:

First, check your BIOS/CMOS settings and ensure that any
onboard Serial/COM ports are disabled.

Second, if your laptop has multiple USB sockets always try
to insert the plug into the same socket. This assumes that the
USB-to-Serial is a USB 1 (Full Speed) device.

Third, you've likely accumulated a number of "Phantom" entries
in your Device Manager ports category. What you need to do
is add/set-value a new System Environment Variable
DevMgr_Show_NonPresent_Devices
and set it's value = 1
Open Device Manager, Click View - tic/check the option box
that says "Show Hidden Devices". Expand the Ports category.
You'll likely find a long list of entries shown in diminished tone
or grayed out. Right Click each one and from the context menu
click uninstall. Do this with the USB-to-Serial adapter unplugged.

You can add System Environment Variables with the System
applet in Control Panel (Classic View). It's found under the
Advanced (TAB).