visa write hangs forever on a compact fieldpoint 2020

[Olaf_Stetzer]

Hi all (crosspost from other forum as suggested by forum member),

I have three devices connected to a compact fieldpoint 2020 via RS232 using
the VISA drivers. Th programm runs smoothly as long as I use only 1 or 2 of
these devices. If I try to use all of them, it runs only for a certain time and then
one loop hangs forever. This loop contains controls for two bath cryostats by
Lauda, the communication is done using their labview drivers which are "normal"
vi's using VISA internally. Whlie debugging I found that the hang is caused
by the VISA-write command. There seems to be no timeout active to prohbit
a hang of this call forever. Is there a workaround for this or a way I could
debug and fix this problem? Unfortunately, it only happens after a while so there
seem to be special conditions on the fieldpoint neccesary to cause this hang.
The only additional information I can provide is the fact, that this "seems" to
happen always on COM3 (I haven't tried to switch ports and devices yet to
test if it is the device or the port) while the device on COM1 (a multi channel
analyser) is transmitting a lot of data. This is done in a second RT-timed
loop which is running without a problem while the other RT-loop containing
the above mentioned driver is hanging.

Thanks for your help,

Olaf

Labview: 7.1 with latest VISA drivers (I hope, those that came with 7.1)
and RT-modules.
Lauda drivers (LD1002) for the proline cryostats were taken from here:
http://www.lauda.de/hosting/lauda/website_de.nsf/urlnames/BMJL-5XNCMN/$file/LD1002.exe

[Aaron_G]

Olaf,

I had a somewhat similar problem with LabVIEW 7.1 (timeout error on VISA write)  and the version of NI-VISA that came with it. There was an upgrade for the NI-VISA that NI was able to provide that resolved the issue. I do not recall the version number of NI-VISA that had the fix. Check the version of NI-VISA on your computer (MAX>>Software). If I recall correctly, the minor revision was incremented by 2 and that is the version that is fixed (e.g. VISA 3.1.2 becomes 3.1.4). That version should be available in the NI drivers download section. Otherwise, contact NI Tech support (www.ni.com/support) for this. 

Regards,
Aaron

[Olaf_Stetzer]

Aaron,

thanks for your suggestion, that helped. I now get error 1073807339 occasionally, but no hangs
anymore. I can live with these errors, so I am happy now. Actually, I first wondered if the library
version was that old on my system. It took me a while to figure out that although the VISA
version on my PC was quite recent, the one on the fieldpoint was still very old. I thought in
the beginning, that compiling and uploading a vi to the fiedlpoint would automatically also update
all used libraries but this is not the case. Only after updating drivers via MAX I could solve the
problem.

Thanks,

Olaf