USB to serial/GPIB conversion connecters

[danwebb]

This may be one for the sales guys but I'll post it anyway. I'm considering USB to serial (or GPIB) converters (such as NI's http://sine.ni.com/apps/we/nioc.vp?cid=11383〈=US or Keyspan's http://www.keyspan.com/products/usb/pdaadapter/ ) rather than standard ports/cards.

I know it is not possible (easily at least) to write drivers for USB devices using Labview so I'm interested to know exactly how USB-serial converters work in terms of writing a serial/GPIB driver in Labview.

If I were to use one of these converters to write a serial driver for an instrument, how is the USB port viewed by Labview or, more specifically, VISA. If you drop a 'VISAresource name' control onto a Labview panel, does it pick up the serial instrume
nt connected via the USB-serial converter automatically? Or does the USB-serial converter come with additional driver software of its own to handle this? Can a driver written using one of these converters still be used on standard RS-232ports / GPIBcards?
Basically, can someone explain simply how the Labview to USB comms works when using this USB-serial converter?

Thanks,
Dan

[Chris_Rake]

Hi Dan,

Both the NI USB-232 and NI USB-485 appear as normal COM ports. So plugging a 2-port USB-232 into a USB port will add two additional COM ports (COM5 and COM6 for example). This is handled by the NI USB Serial driver. Once the COM ports are added, you can make VISA calls to the USB serial ports as if they were local (COM1 or COM2). Just make sure you have the USB serial adapter plugged in before running LabVIEW or else VISA may not recognize the new COM port.

Also, I should add that the NI USB adapters have been extensively tested with NI-VISA and LabVIEW.

[Sanjay]

Usually USB-serial converters come with additional driver software that makes the operating system see additional serial (COM) ports that will work as usual (transparently) - i.e. any regular (Win32) serial application will work (including VISA-serial, which must use Win32 to be able to control all standard operating system serial ports).
(The above assumes you're using Windows.)