Prologix GPIB-USB opinions please

[GonzoTech]

Hello All,

I'm considering getting a Prologix GPIB-USB interface. I would like to ask for some opinions from users of this device.

Thanks,

Mark

[Dennis_Knutson]

Surely you did a search for 'Prologix' before posting your question, didn't you? You would have found numerous posts and my opinion on the device.

What programming language will you be using it with and what instrument(s).

[GonzoTech]

Yes, I did "Google it". I'm hoping that someone has got this thing to work! I'll be using LabView.

Thanks for the reply,

Mark

[Dennis_Knutson]

No. Use the search tool here. Or click on the link I just gave you.

People have gotten it to work, though some inexperienced users have struggled. If you use LabVIEW and want to use any one of the thousands of available instrument drivers, you will have to do at least some modifications. You will have to do quite a few modifications if you intead to talk to multiple instruments. You will be communicating at serial port speeds and not GPIB. The max data rate of standard GPIB is 1Mb/sec. The best serial baud rate is 115k.

If this is for your own personal use and you don't have a monetary value for your time (i.e. it's not job related), then it is probably worth it.

[GonzoTech]

Dennis,

Thank you so much for taking the time to help me and for the "heads up" about transfer speed. Yikes! I'll look into it further.

Mark

[prologix]

Maximum transfer rate of Prologix GPIB-USB is closer to 500kbps. It uses the FTDI FT245R USB-FIFO chip (not the FT232 USB-Serial chip) and is therefore not limited to the usual serial baud rates.

[JasonSmith]

I normally don't correct anything Dennis says, because in most cases he is correct. In this case, he should have had a capital 'B' when communicating the GPIB transfer rate.

Most NI GPIB interfaces can communicate at more than 1.5 Megabytes per second. The actual throughput depends on the size of the packets you are transferring, bus topology, and the instruments you are talking to.

A standard serial port will transfer at 115.2 kbaud, so with normal serial framing you will only achieve a theoretical maximum of 11.52 kbytes per second. 500 kilobaud only gives you 50 kbytes per second, and that doesn't account for the latency of getting the commands across the USB bus.

NI-488.2 with a PCI-GPIB can achieve higher transfer rates than this, even if you are only transferring 2 bytes at a time.

-Jason S.

[Dennis_Knutson]

Thanks for pointing out my typo. The 8 parallel data lines make a big difference when using a real GPIB controller.