CVI serial comms program does not work with a serial to USB adapter

[src75082]

I still haven't determined what is causing the duplicate data. It looks like it is an exponential relationship between the baud rate and the errors on my adapter. At 921.6k baud, I get about errors about 50% of the time, at 460.8k baud, I get errors about 20% of the time, and in the latest test I ran at 230.4k baud, I only got 1 error in 10,000 iterations. I still haven't seen any duplicate errors at 115.2k, but I'm going to let it run during the day and overnight tonight to see if I ever get any errors at 115.2k (unless I can think of something else to try, or my computer crashes 🙂 ).

I sent an e-mail to Saelig, just to see if they were aware of any issues with receiving duplicate data, but I still haven't received a reply. Maybe I should just go ahead and contact FTDI directly as well.

[Wendy L]

Hello src75082,

Regarding your questions:
"Has anyone been able to successfully use a USB to serial adapter with the CVI serial library, and if so, which adapter did you use?" and
"Can someone at NI, or elsewhere, please verify whether or not nonstandard baud rates (or baud rates above 256k) are supported by the RS-232 Library?"

I testing the behavior with the NI USB-232 and the NI-Serial driver. I was able to communicate and run the CVI shipping examples at the default rates.

You should be able to configure the port with OpenCOMConfig at baud rates above 256k. CVI does not limit the baud rate, but instead, the available baud rates are limited by your system / hardware capabilities, as documented in the following KnowledgeBase.

As you mentioned, contacting your vendor would be a good idea. In order to verify that the issue lies with your driver, you could create a simple application without the CVI RS232 functions, but instead, with Windows SDK functions. I suspect the issues you are seeing with duplicate data would still occur.