Detecting USB serial adaptors using VISA

[JimPryle]

Hi,

In recent LabVIEW (7.1) applications, I have used the 'VISA Find Resource' function to return a list of available serial ports for the user to select their preferred port.

This works fine in general, but doesn't seem to work at all when using a USB-serial adaptor. When using such an adaptor, the assigned COM port is visible in the Windows device manager but not in NI MAX.

Unfortunately, RS232 serial is seen as a legacy interface and people (particularly laptop users) are increasingly using USB adaptors for serial functionality.

Does anyone have any ideas how I might detect and access a serial COM port adapted from USB?

Any suggestions gratefully received.

Jim P.  

[Dennis_Knutson]

What's the make and model of the adapter? I've used a couple different types with no problems. Other users have reported the same problem with some others.

[JimPryle]

It's an ATEN UC232A.

(http://www.aten-usa.com/?product&cat=595&Item=UC232A).

We should have some different adaptors around, so I'll try to borrow another one to try it out.

Jim P.

[JimPryle]

Hi again,

I can see the COM port for the USB-serial adaptor now.

I deleted some ald aliases from the visaconf.ini file and this seems to have made the port visible, although I'm not sure exactly what it was in the alias definition that upset it beforehand.

The only real difference I can see between the alias data in the old visaconf.ini file and that generated when I re-ran my LV app was that COM5 (the USB-serial adaptor) previously had 'Static5=1', whereas the corrected file has 'Static3=0'.

Jim.