USB to serial coverter and CVI

[PC Programmer]

Has anyone tried to interface FTDI USB to serial converter via a Virtual Comm Driver?  It seems to have a problem with incorrect string length (but I can't tell whether it is transmit or receive...) as I'm getting a few timeouts and a bunch of invalid length errors.

Also, what converters are reliable?

[Makoto]

There are so many kinds of USB-Serial convers sold in market, and not all the converers work fine as you expect.  Before using it for instrument control such as through VISA library, try the converter with the Hyper Terminal at the desired communication param settings (baud/data/stop/parity/flow, etc) connecting your instrument. 

[test_man]

So far I have tried 2 USB to serial convertors but none of them is great.

Prolific does not work well. It crashes PC more frequently. I think it has issues with USB drivers.

Aten works ok but some time it crashes my PC without any warning. My PC just restarts.

Anybody else using better one?

[John Cameron]

In message <1123256476874-251111@exchange.ni.com>, Sheetal <x@no.email>
writes
>So far I have tried 2 USB to serial convertors but none of them is great.
>Prolific does not work well. It crashes PC more frequently. I think it
>has issues with USB drivers.
>Aten works ok but some time it crashes my PC without any warning. My PC
>just restarts.
>&nbsp;
>Anybody else using better one?
>&nbsp;

Assuming we are talking about embedded applications and not just virtual
RS232 dongles;

I have used the Silicon Labs CP210x. They are USB to UART bridges.

As standard it comes with driver software to use as a virtual RS232 port
(but be wary if you want to use a coms break signal). Or you can use it
with SiLabs USBXpress library (DLL and header file). I've used it both
ways quite successfully with CVI.
--
Regards,

John Cameron.
Type softly, read gently.

[PC Programmer]

Thanks for the recommendation.

However, I initially tried the Silicon Labs CP2101ED Eval Kit and it worked flawlessly in the short time I tested it.  The reason I switched to the FTDI part was because the SL part is a leadless chip carrier package and it is difficult to hand assemble or prototype with.

I did receive a response from FTDI.  They recommended this document which has helped a lot (so far):

http://www.ftdichip.com/Documents/AppNotes/AN232B-04_DataLatflow.pdf

Thus far, tweeking the chip's parameters using their VCD via Windows XP's facilities in device manager has proven successful. 

I set the data size to the smallest (given the low baud rate), left the timer at 16 mSec, set the timeouts for send and receive to 100 mSec each.  I also followed their advice and set flow control to XON/XOFF.

Time will tell...

[craigherdman]

Of course you can always look to NI for your USB->232 needs! Our USB-232 is guaranteed to work with all NI software including NI-VISA. For more info see here:

http://sine.ni.com/nips/cds/view/p/lang/en/nid/12363

Craig H.

[test_man]

Yikesss.........that $150 hurts!!!!! :)

[craigherdman]

---

@sheetal wrote:
Yikesss.........that $150 hurts!!!!! 🙂

---

Aha! It may seem so but coupled with world-class support from National Instruments Applications Engineers and guaranteed compatibility with NI software, such as VISA, it's not so bad! You have to watch out; since there are so many vendors that produce USB to serial converters you may run into a bad apple here and there with respect to full 232 implementation. See the following Knowledge Base Article for an example issue:

Error -1073807298 When Using a Third Party USB-Serial Adapter

Now this is not to say that you can't use third-party USB-Serial devices! Just buyer beware since some really cheap ones fail to fully implement the same calls that a built in port does. But with NI's USB-232 you will not see those problems ;).

Craig H.