FTP with VISA/IVI instrumend driver

[Tegich]

Hello everyone!

Maybe this question may be somehow stupid, but I need to be sure. The question is: Is it possible to use the FTP protocol within an IVI instrument driver?
I have to transfer files over Ethernet. Now, without an IVI instrument driver, all commands are send with TCP/IP and the file is send after that by FTP.
Does using now an IVI instrument driver mean, that the file should be send by TCP/IP or can FTP still be used?

Thanks for any answer!

Greetings,
Thien

[NathanT]

Hello Thien,
      Since IVI drivers use VISA, the better question might be: "Is FTP supported in VISA?", before looking into that, please explain in detail what you would like to accomplish with FTP in your application.

1.  Would you like to programmatically instruct your instrument to FTP a file to or from an FTP site?
2.  Would you like to send or receive a file from your instrument by using the FTP on your computer?
3.  What instrument are you using?
4.  Are you developing your own IVI driver?
5.  What Development Environment are you using?
6.  Any additional information about your application as it pertains to the instrument, IVI driver, or FTP usage would be helpful.

Cheers,

NathanT

[Tegich]

Hi NathanT,

thank-you for quick responding.

I will try to explain my question a little clearer 🙂

1. We are developing instruments. Now the firmware uses FTP to transfer files and TCP/IP for all other commands.

2. Transferring files between the Computer and the instrument in both direction is now done by FTP

3. This are some kind of measuring instruments which are using files with instructions

4. Yes, now our old communication methods should be replaced by IVI drivers. So we maybe need to change the firmware of the instruments, too.

5. LabWindows/CVI

6. How do other transfer big files with IVI drivers? Our firmware specialist says it’s standard to transfer files with FTP and not by TCP/IP. If we want to use IVI drivers, should he change the file transfer to work with TCP/IP or not?

Thanks for any help.

Greetings,

Thien

[Dennis_Knutson]

It's unusual for any type of instrument to perform file transfers of any type and there is no mechanism for file transfers in any of the IVI classes. What is the class of instrument you are developing and what is the nature of the files you wish to transfer?

For communication related to Ethernet instruments, you might want to google the VXI-11 standard.

[Tegich]

The files are XML, pure text files. With GPIB (which we also use) the files are transferred as normal data which are read by the standard read or scanf methods of the IVI driver. For the GPIB mode we didn’t have to change the firmware to work with the new IVI driver. But in Ethernet mode the files (and only the files) are transferred by FTP.
What should be done to bring the instrument to work with the IVI driver? Should the firmware changed?

It's an IVI driver for general purpose.

Message Edited by Tegich on 08-20-2007 09:23 AM

[Dennis_Knutson]

In other words, the instrument is part of any defined IVI class and you just used the IVI wizard because it was convenient.

Seems to me that you can do whatever is most convenient. Based on the VISA resource name, you can determine the type of interface and either do a regular file read or implement an FTP transfer in CVI. I haven't used CVI for that and don't know how easy or difficult that would be. I did a quick check of the CVI board and there are a lot of threads on implementing FTP with CVI. Imho, it should be transparent to the user, though. In other words, if in GPIB mode, the user only has to provide a path to the driver, with an Ethernet connection, the user would do exactly the same.

[NathanT]

Hello Tegich,
       Thank you for answering all of the questions that I asked.  I think that Dennis has brought up some very good points.  If you are not planning on implementing the full IVI specification in order to take advantage of:

1. Interchangability
2. Simulation
3. Range Checking
4. State Caching

     Then you would probably be better served by a CVI Plug and Play Driver.  If your previous driver used VISA to communicate over GPIB and just sent the files as strings, then it should work over TCP/IP.  That is the beauty of VISA.  Since you are just sending text already, I do not see a compelling reason to complicate things by adding FTP. 

     On the other hand, you and your colleagues know your instrument and its firware the best and you might have an instrument command in which you just pass the folder address where you want the file transfered and then let the instrument do that.
      It sounds like an interesting application.  Let us know what you end up deciding on.

Cheers,

NathanT
  

[Albert.Geven]

I support Nathan in his view of IVI.
If IVI is working correctly, and in Windows it sometimes does, then the only real problem left that debugging is hard..
If it is not working that point strikes even harder.

In my opinion are the new project drivers better, the only exception being statecaching that is difficult to implement without a central entry point for a driver.
To get simulation a simulation driver for an instrument should be developed and with the new LabVIEW LIB structure (not an llb) it should be able to replace a driver in an application by a simulation driver.
The biggest problem however will be the maintenance of the project drivers for popular instruments.
It is very difficult to give them the same basic interface as IVI classes of instruments have.

I hope that NI (with the help of people everywhere) succeeds in building such project drivers.
Drivers that work good, are easy to debug and show a good way of LabVIEW programming as examples for other drivers.

[Tegich]

Thank-you very much for helping.

Now, I decided to use the function InetFTPAutoRetrieve and InetFTPAutoSend which are available in LabWindows/CVI.
These functions I implemented into the IVI instrument driver. And it works! Without changing the frimware of the instrument 🙂
Sure, now it’s not a really a VISA IVI instrument driver, because FTP isn’t part of the standard.
The other way, changing the sending method of the files to TCP/IP would end in a loss of performance, because FTP seems to be faster in transferring big data.

Greetings,

Thien

[Albert.Geven]

Hi

I doubt that ftp is faster then tcp/ip because ftp is built up on tcp/ip!
but it is using tcp/ip maybe in a faster mode.