[BALU] Query regarding comm ports in windows

Hiram Lester Hiram.Lester at compassbank.com
Tue Dec 16 15:57:19 CST 2008


I can't speak to the ability to do this programmatically, but from the couple of times I have used such adapters, I have observed the same behavior of the COM port number changing from one time/port to another. Are cheap serial cards an option or do these machines actually have the com port header on the motherboard and just not exposed to the outside world?

>>> <andrew at asi-web.com> 12/16/2008 3:35 PM >>>
I've got a small problem relating to windows-side comm ports, and I'm  
hoping some of the windows-afflicted on the list might be able to help  
me figure it out.

I've got a program written in Delphi (think Visual Pascal) which  
requires a serial connection to download information off of a handheld  
unit.  Some of the people who will be using the unit are using systems  
which don't have serial ports, so I was asked to test a serial to usb  
adaptor cable alongside working on the program.

The serial/usb cable works nicely, but it's causing a problem for me.   
Because there are third-party uploader/downloader programs being  
invoked, I have to be able to specify which serial port I'm using to  
download from the handheld unit.  But the user has also requested that  
the cable needs to be shiftable - that is, that they can swap it from  
one USB port to another without having problems running the program.   
And this particular cable seems to swap out comm ports when swapped  
between USB slots.  (That may be inherent in the way usb ports work -  
I don't know enough about them to tell.)

I can, manually, go investigate the device manager and see which port  
is being assigned to the cable.  Is there some way to duplicate that  
effect in code from behind the scenes, and what would be the best way  
to go about doing that?
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