What is the different SRS-232 and GPIB by using Labview?

[whuili]

Hi, I have question : I hope to use labview program to control some instruments and the interface of them is RS-232. What is the different SRS-232 and GPIB by using Labview?Thanks.

[Dennis_Knutson]

Are you wanting to know the differences in programming RS-232 and gpib instruments? If that's the case, then the answer is, there doesn't ahve to be any difference at all. If an instrument driver is designed correctly with VISA functions, then that single driver will work for gpib, serial, vxi, pxi, etc. instruments. There used to be a separate set of functions for serial communication by NI has dropped them from LV7 and only supports VISA now. You may find some older instrument drivers that use the gpib function calls but it's very easy to convert to VISA if you need to use them.

[JuanCarlos]

Hi,

There are a many differences between these protocols, however programming them in LabVIEW is almost the same. Here are some key differences:

+232 is a 1-to-1 connection; GPIB allows up to 15 devices on 1 GPIB bus.

+232 is slower than GPIB, 232 uses 1 single line to transmit and 1 to recive. GPIB has 8 data lines.

+Longer cable throw with serial; GPIB has a maximum of 4 meters between devices.

These are some of the features that will help you go for one protocol or the other. In LabVIEW programming there will be nimor differences only.

Hope this helps.

Regards,
Juan Carlos
N.I.

[Ben]

I believe the max RS-232 cable run is actually 50 feet.

I have seen it run farther than 50 feet but if you want to high baud rates, 50 feet is the limit on the spec.

Beyond that you should switch over to RS-485.

Ben

[whuili]

Hi,
Thank you for your answer.

You mean in your answer that I just control one instrument by using 1 computer with 1 RS-232 port, right?

If I use GPIB style to control instruments, I have to install a GPIB card into my computer. How about RS-232? Need I install any card for RS-232? Thanks.

[Dennis_Knutson]

Almost all computers have at least one RS-232 port. You may have either 9 pin or 25 pin DB connectors for use. Your OS's hardware report will tell you how many you have. If you need to control more instruments than ports you have, additional RS-232 cards are pretty cheap. Some have multiple ports on a single card. I have used one called RocketPort that has 8 RS-232 ports on a single PCI card. I don't remember the price right now. The other option is to use USB to RS-232 adapters. These are pretty inexpensive as well.

[Ben]

"Almost all computers have at least one RS-232 port"

Have you gone shopping for a laptop lately?

Serial ports are being replaced with USB ports!

Ben