VISA TCPIP can't successfully send arb waveform size > 4054 to wave generator.

[jae]

I have an AG33220A waveform generator and was looking to convert the drivers from GPIB to VISA so I can take advantage of the ethernet port. However, VISA TCPIP can't successfully send an arb waveform with size greater than 4054 to arb waveform generator. A Waveform download of size > 4054 is successful if use a GPIB write or VISA GPIB write. It only seems to be an issue if we are using the TCPIP connection on the instrument and using VISA TCPIP and the waveform size is greater than 4054. We were able to reproduce the problem using a C++ code example acquired from Agilent. The NI-VISA dll is the installed one and we can't find the Agilent visa.dll to extend the comparison.

I've tried both increasing the timeout and increasing the VISA I/O buffer and it still fails at the same point. It doesn't seem to be the Labview end so much as something in the TCPIP implementation at the visa.dll level. I understand that TCPIP has a packet size limitation of 4096 but as I understand it the protocol should break up the data into multiple packets of that size or smaller.

[Doug M]

jae,
First, I would make sure you are using the latest NI-VISA driver, version 3.3.  If you are using this version and are experiencing this problem, I would try doing an NI-SPY capture while running your program and seeing if it reveals any errors.  You could post the NI-SPY capture as well.

[tds]

Hello Doug,

I can confirm jae's problem with the visa driver 3.3. Attached a short sequence. Increasing the cycle number of the loop shows the problem. Remark: The problem with the Agilent 33220 occurs only every second access.

Regards Bernhard

[JasonSmith]

I do not have an instrument to actually try this with, so I have tested the limitations of the VISA Write when using a VISA TCP Resource.  I can successfully transmit at least 15 megabytes with a single VISA Write without problems.  I am currently using NI-VISA 3.4.1, so I would recommend that you upgrade to the latest version and see if the behavior persists.

NI-VISA Current Version

Jason S.
Applications Engineer
National Instruments

[JoshuaP]

We have actually been able to reproduce the problem. We are working on a fix and hope to have it available soon. I'll let you know as soon as it becomes available.

Josh Prewitt
National Instruments

[JoshuaP]

Sorry for the delay. NI-VISA 3.5 has now released and should resolve this problem. It should be available for download from www.ni.com soon and it is immediately available at https://download.ni.com/#support/visa/drivers/win32/3.5/

-Josh