Upgrading MAX 3.0 slow down serial comm. Any known issue?

[LegalEngineer]

After upgrading MAX to 3.0 and TestStand to 3.0 LabView VI using Serial Com failed. By putting delay second between write commands the problem got fixed. It seems like the MAX 3.0 causes delay in Serial Comm. Is there any known issues?

[Ram2003]

I am not aware of any issues with upgrading to Max 3.0
However, I have come across this problem even with eralier version of MAX. I have created VIs without any time delay between serial write VIs and noticed that some times (Not always) visa write function returns an error.

So, I always use visa write VIs to send a serial command, insert a time delay function in a sequence structure, create property node to read number of bytes available in serial port and then call visa read VI to read the serial port. This architecture worked for me so far all the time.

Just a suggestion. So I think this has nothing to do with MAX.

[Ben]

No nessesarily MAX,

but

NI-VISA had a slow down issue in one version. If you are using NI-VISA then down load the latest and greatest.

Ben

[Evan]

I am not sure I understand the question, so I will restate my interpretation. If I am off, let me know so we can get the issue resolved for you.

You recently upgraded TestStand along with some of the drivers. Most notable would be that VISA was upgrade, and therefore MAX got upgraded. After the install your serial application stopped working. However you discovered that adding a wait between the writes and reads has fixed the issue.

If the above is correct than you are unfortunately dealing with expected behavior. We are constantly striving to increase the performance of our software. In this application VISA has become faster, and therefore is able to send your instrument more commands faster. There is then a good chance that your instrument is just g
etting bombarded with commands faster than it can process them. Thus you get the errors, and this also explains why the delay fixes the issue.

Evan
National Instruments

[LegalEngineer]

What you have restated is correct about installation part. How it was discovered is as follows: Before the install program was allowed to write, say, 10 commands in a row without any delays in between. After the install the program didn't work unless what was in the write buffer got cleared - in this case read it back - before writing another command. Between write and read there is no delay, however the additional reading back now delays the time between write commands.

I think your explanation about the new VISA performing faster makes sense to me now. The serial communication got relatively slower compared to a faster NI-VISA performance. I was thinking the other way. Upgrading MAX would have probably updated the VISA.

Thank you for the corre
ct answer.