usb-to-serial VISA read problems

[comoyer]

Hi,

 I'm trying to control several mass flow controllers that are attached to a Alicat BB9 serial hub. The hub is then connected to the computer via RS-232 serial. The computer this is being done on does not have a serial port, so a serial-to-usb adaptor is used. When plugged in, the computer (running XP) recognizes the serial-to-usb and asks for a driver. I have installed a driver from the manufacturer of the adaptor, downloaded from the internet. The same driver is used on another computer (running Vista) with no problems.

I am able to verify that the device is installed and working correctly through Device Manager. Also I am able to view which COM port the device is on. Opening NI's Measurement and Automation Explorer (MAX) I am able to see the COM port listed under serial devices. I am able to validate port settings and open a VISA session with the device. However, any time I try to read from the device it times out. I get the error xBFFF0015. I have been able to up the time out setting to 5000 and 10000 with no change.

When running a VI that is used around the lab to control the same setup, I can trace the error back to a VISA read subVI. The 'read buffer' returned doesn't have a value and triggers an error. I can plug the USB into a laptop that has the same VI and it will run with no trouble. The 'VISA read' subVI does return a value when running on the laptop.

I am running LabView 8.5 and VISA 4.4. 

If anyone has a suggestion that could get this working I would appreciate it greatly. Also, I'm a grad. student working on this and my understanding of LabView isn't terribly great, so dumbed-down responses would be nice   🙂

Thank you for your help.

Connor

[Justin_E]

Hey comoyer,

0xBFFF0015 is generally a serial timeout error, so upping the timeout setting is a good first step to try and resolve your issue. Have you tried communicating with your device through Hyperterminal or through a test panel in MAX? To get to the VISA Test Panel, open up MAX and navigate to your COM port. You should be able to click on "Open VISA Test Panel" to open a test panel for this COM port. Try writing and reading to/from your device with these applications to see if you still get the same error. 

When you plug the serial-to-usb adaptor to your laptop, is everything configured the same as it is on your desktop? What operating system is on your laptop?

[comoyer · Accepted solution]

Thank you for the follow up. However, I was able to solve the problem already... It was simply a driver update that fixed my problem. The driver being used is 'Prolific usb-to-serial' and was version 1.something. I updated to 2.0.2.1 and it works fine now. I thought I had updated to the most recent before and apparently I hadn't... kind of retarded. But thank you anyway!

[Justin_E]

Haha, no problem. Glad to hear that you got it resolved

[swsyoon]

Hi, Connor,

I'm using the same setups with yours and I have difficulty in figuring out communication problem between Alicat mass flow controllers and computer.

Can you provide your email that I can contact to? I'd like to ask some questions. My email is swsyoon@gmail.com.

Thank you.

Yoon