DAQmx Read Frozen

[ivto]

My system: PXI-1031, PXI-8184, PXI-6225, PXI-6221, LV RT 8.2, Win XP

My system contains a PXI box as the real-time target and a PC as the host.  In the LV RT program, there are multiple timed loops controlling multiple channels.  The problem is, once in a blue moon, one of the timed loops/channels locks up and damaged some hardware.

After using the "Write to file.vi" to log some text messages locally to the hard drive of the RT system, this problem, or at least the same symptom, happens every time.

The last logged message was placed before a "DAQmx Read Analog", and the message after the "DAQmx Read Analog" didn't get logged.

So I assumed that the DAQmx Read was frozen when the system was busy performing file I/O, as file I/O takes a lot of system resources.

Without the message logging (File I/O), I suspected that the lockup was caused by occasional high Ethernet traffic (updating network enabled shared variables and etc). 

Why does "DAQmx Read" lock up (the default 10 sec timeout didn't work) while system is busy and how do I prevent it?

Thank you for your help.

[samantham]

Hello,

Are you getting an error message or is the DAQmx read just hanging?  Please note that proper wiring and handling of Error In and Out Clusters will help with tracking errors.  It can also help control the flow of execution.  Please provide a screenshot of the error code, if you are getting one.

What sample rate are you using?  I would suggest trying to slow down the rate to see if the problem still happens.  Please try this and it will help with the troubleshooting process.  In addition, please take a look at the task manager to determine the CPU usage while program is hanging or throwing an error. 

I would be interested in seeing an example version of your code.  It might help resolve the issue and I will have it handy in case it is needed.  Please attach a simplified version of the code that reproduces the issue. 

[ivto]

I had an Error Out Cluster but no error message returned so that was why I suspected that the DAQmx Read was frozen.

Three analog channels were assigned to the task and each one was running at 60,000 samples per second.  I will try to slow it down to see if it improves.