USB-6211 with DAQmxBase 3.3 has to be restarted after access with LabVIEW 8.2

[Bryan]

I have DAQmxBase 3.3 and LabVIEW 8.2 on a Slackware 13.0 system with kernel 2.6.24.5.  I also have two USB-6211 modules.  We are trying to set them up with continuous output waveforms.  It has worked some - we were able to get the 4 waveforms programmed and running.  But we often find that when we program the devices they will "disappear" - lsdaq will return an error -6005 and we have to unplug and replug both of them to try again.  www.ni.com/info reports that this may due to premature termination of an operation.  But we have a set of VIs that program everything and start the output, then just go into a while loop to wait for user input before terminating the output.

Has anyone experienced similar behavior with USB devices?  Any ideas on what may cause this type of behavior?

Thanks in advance.

Bryan Peterson

bryan_peterson@byu.edu

[JoeFriedchicken]

One possible explanation for the behavior you're seeing is that the task controlling the first device is interfering with the task controlling the second device. DAQmx Base, unlike DAQmx, is not multithread-safe [1], so all of the code making hardware calls needs to be in a single thread. In LabVIEW, single-threaded programming with DAQmx Base can be accomplished by using only one error cluster to connect all of the DAQmx Base VIs. Without a description or screenshot of your code, I cannot say for sure either way 😉

[1] NI-DAQmx Base 3.3 for Linux readme

http://ftp.ni.com/support/softlib/multifunction_daq/nidaqmxbase/3.3/Linux/readme.txt

Joe

[Bryan]

This appears to have cured the problem.  I need to be more careful about sequencing in the future.  Thanks for your help.