PDA crashes after about 20 measurements or 15min working

[FReich]

Hello everyone,

I use a Dell Axim x51 with 624MHz and 64 MB SDRAM. The DAQ Card is a NI-CF6004 Compact Flash Card.

512 Samples are aquired with 1024 Hz and a FFT analysis is run to gain the Frequency domain.

The data is aquired with the VIs of the DAQmxbase group I have this VIs in the Trigger loop as well as in the measurement and FFT calculation sequence.

The programm works like that:

A trigger loop is always running to measure the signal at any time.

If the signal exceeds a certain value then the loop stops and starts the measurment and FFT calculation.

The problem is that this programm just run for about 15min or for about 20 measurements. Then the PDA doesnt react anymore and I have to restart.

Does anyone have a clue about this kind a problem?

Yours

Franziskus Reich 

[Greycat]

Hi FReich:

Couple of things I can suggest you do without being able to see your code.  Sounds like it may be a memory leak.  Monitor the memory usage while the program is running, there are some handy memory vi's built into PDA that can be used, if the usage continues to grow, you may have a memory leak.  Also, you could try to remove parts of the code one at a time, and when the problem goes away (if) you might have some clues as to what is causing the problem.  You may concider posting your code, this way someone can actually look at what you have done.  You will probably get more help if you post the code.  Just a couple of thoughts ... hope this helps.

Greycat

[FReich]

Hello Greycat,

I monitored the memory and as you said, I have a memory leak.

How does such a memory leak occour?

Yours

Franziskus

[FReich]

I found the responsible part of the programm.

If this loop is run, then the memory usage increase steadily.

Maybe someone could give me some suggestion. Every idea is greatly appreciated.

Many thanks.

Franziskus

[FReich]

I have  to  report something  strange,

to post it at this forum I sorted the connections to make them tidy and now I deployed it again and tryed it on the PDA.

It seems Ok. ???

I post now the version I had before, which the problem occourt everything is the same I just tidied and get red of the part on which  I put a red circle.

Can it be that a leak can  occour if some VIs are a little front or  back or.....

or I am just mistaken and will continue to have that problem with my other versions?

yours

Franziskus

[Greycat]

FReich:

Thats very interesting.  I started thinking about this and realized that I had totally missed a possible reason for the increasing memory usage.  Sometimes, when not careful, one can set a loop to run to fill an array lets say, but acidentally have it run infinitely or build on itself every iteration which will also use up your memory.  Nothing I can see in your code would cause such a thing.  One thing I do notice is that you start and stop the DAQmx everytime your loop iterates.  Are you sure this is what you want to do?  Try to put the start before the loop and the stop after and just read it every iteration, this might clean things up a little.  Might not do anything to your fix your memory filling up.  You might want to post your code so other can have a look, or try to reproduce the leak with absolute minimal code, then get the attention of an NI engineer on here, they're very good about testing bugs and sending them to R&D to be fixed.

Greycat

[FReich]

Hi Grey,

You are totally right about your suggestion to put the start before and the stop after.

I contacted a NI engineer and according to him the bug is inside of the DAQmxbase VI. Everytime I read from the DAQ device I get some leakage.....

It should be fixed with the Update 8.2.1. I am now going to  update and hope it will apply for that problem.

Thank you.

Do you know a possiblilty to start the trigger within the DAQmxbase.

I saw inside the DAQmxbase task configuration tool the possibility to select a trigger. However I dont know if its a trigger like I think.

I want to trigger the measuremnt when the amplitude exceeds a certain value.

Yours

Franziskus

[Greycat]

Hi FReich:

    Good to hear you are on your way to solving your problem.  Please be sure to post if the update fixes the memory leak ... I'm sure there will be others that will be interested in the future.  If it does not solve the problem, be sure to contact NI and have them reproduce (and hopefully fix) the bug ... As far as using triggers in the DAQmx, I have never used triggers before so I can't really help you out on that, but I'm sure what you are trying to accomplish can be done.  There are certainly some good examples in labview around using triggers, I would start there.   Good luck.  Let us know how things work out.

Greycat

[FReich]

I have good news.

The Update from 8.2 to 8.2.1 fixes that bug.

Yours

Franziskus