I have a VI that works with a serial port but not with a USB port. why not?

[JoeBlack]

The ports work fine with my other utility programs using the same hardware configuration. My hardware communicates through RS232.

[JoshuaP]

Hey Joe,

I'm not exactly sure what hardware you are using, but I am going to assume that when you mention the USB port you are talking about using a USB to RS232 converter. My first questions would be what is the model converter are you using.

I know the NI USB-232 converters work flawlessly and are designed so that they show up as a native serial port under Windows as an additional serial port and fully support all of the same commands.

Be aware of cheap converters that may not fully support all of the functionality found in built-in serial ports or ones that use cheap drivers. These cheap converters may not be compatible with VISA or your hardware.

As a test I would recommend opening up the Windows Device Manager and first make sure that the add
itional serial ports show up. Next, open one of the Windows applications like hyper terminal to see if it is able to communicate with your hardware. If this fails I would recommend using a different USB to RS232 converter or contact the manufacturer for assistance. Let us know if you are using an NI USB-232, what OS you are using, or if you are connecting the USB port directly to your device without using any RS232.

-Josh

[JoeBlack]

The OS is XP. Yes, I'm using a USB to RS232 converter, not sure of the brand just yet. The ports do work with other communication utilities. Yes, they do show up in device manager as a COM port.

Other customers are having problems using Labview7.1/XP/USB to RS 232 converters.

[JoeBlack]

I got it to work...I did not load the drivers on my laptop because "I thought" it would not need them just to run a serial application, apparently it does.

[reijvargas]

i got the same problem, but my drivers are fully installed, and im testing the device with HyperTerminal and it doesnt work.

Im using a U232-P9 conversor and Windows XP and in order to test im seding a string trough the port as this "1234567890" but im recieving this "g3f™™2dLÌ " i checked all parameters. This works perfectly with a normal Serial port but with the u232-p9 i have the same problem in LabView as in HyperTerminal.

[Dennis_Knutson]

Have you tried a simple loopback test by connecting the td and rd lines (pins 2 and 3) together? If that doesn't work in Hyperterminal, then you should contact the vendor. If that test fails, I would suspect a faulty driver installation or a faulty device.

[K C]

Hi,

I have to add the 'set buffer size' function to get my USB-RS232 ports running.

If I don't use this function I get a error when I write data to the port.