Instrument Control (GPIB, Serial, VISA, IVI)

Showing results for 
Search instead for 
Did you mean: 

COM-Ports of PCIe-Card do not work


Hello everyone,


I need two COM-Ports (RS232) for one of my applications. Thus, I want to use a PCIe extension card (which provides two additional serial ports besides the internal port:;74;110&PLine=74



My problem is that I cannot use these additional ports in Labview. They are displayed but nothing can be sent or received. I checked a device at the interal port and it works without any problems but with the additional ports it does not work. I have the same problem with the VISA test panel in MAX.

I checked the functionality of the additional ports using my test device and a serial port monitor and this seems to work without any problems.


Does anybody have an idea why labview does not work with the serial ports provided by PCIe card?


Thank you very much and best regards,


0 Kudos
Message 1 of 4
The ports are displayed where? In MAX? If they don't show there, you have no chance of using them in LabVIEW.

What is your os and what version of NI-VISA do you have installed? Do you get any error codes/messages when you try the test panel?
0 Kudos
Message 2 of 4

It looks like a setting issue. Check for the COM port settings (Baud rate, data bits, parity, stop bits and flow control) of the additional ports. Check particularly the flow control settings.


It looks like your hardware is fine. LabVIEW and VISA Driver also seems to be fine since LabVIEW able to communicate to your device using the internal COM port.


Check the settings difference between the internal COM port and additional COM port either in MAX or in Windows Device manager.

0 Kudos
Message 3 of 4

There are a few things you need to look at:

  • First.  the native COM port operates at 12 VDC the PCIe device supports 3.3/5V.  (There is probably a jumper)  Can your device work with this voltage level?
  • Second is the port configured for RS-232, RS-422 or RS-485?  Again there is probably a set of jumpers on the card.
"Should be" isn't "Is" -Jay
0 Kudos
Message 4 of 4