USB comm to a 9 Pin device

[Eyecheck]

I have a device that we sell and a LV application (built using V5.1) that is a 9pin serial and receives simple ascii commands and ships back ascii data. With the demise of the 9 pin, many of our users have gone to a USB to 9 Pin adapter and all works ok. Lately, we have been getting intermittent results on newer operating systems. Basically, sometimes the communications occurs and sometimes it does not, even on the same PC/device. I am looking for suggestions of what might be going on and possible solutions. Thanks is advance for any help.

[drval]

I suspect that the difficulty you're experiencing relates to the device and driver that you are using for the conversion.

We use the Keyspan "High Speed" Serial-USB device (Model 19 Q) for this conversion and have had no problems with it at all.

A URL for further information is:

http://keyspan.custhelp.com/cgi-bin/keyspan.cfg/php/enduser/std_adp.php?p_faqid=2&p_created=1009405039

[Chris_Rake]

Chances are that you are having problems with the hardware. We've seen problems including dropped data in several different brands of adapters.

However, NI offers USB-232 and USB-485 adapters along with an entire line of serial adapter products, and Win32 API and LabVIEW communication tests are part of our extensive product testing. Also, the products are fully supported under Win2k and XP.

[eyecheck2000]

Other than the multi-port output, what differences are there between the USB-232 and single-port USB-to-RS232 adapters (such as those you can get on-line for ~ $40)? What additional features does NI supply in the USB-232 compared to these single-port devices?

[Chris_Rake]

The NI USB-232 boxes support both DTE and DCE operation modes in addition to an "Auto232" mode that simplifies cabling (null-modem? straight-through? doesn't matter!). Also the USB-232 has indicators for transmit, receive, error, and signal validity which aides device communication development. In addition NI's serial products support 5,6,7,8 data bits, NOEMS parity, and RS-232 baud rates up to 230.4k with a driver architecture designed from the ground-up to support the higher serial bandwidth.

These features are all in addition to the world class support that differentiates National Instruments from other vendors.