05-07-2012 08:26 AM
Quick question:
I have created a DO task in DQmx. It outputs a digital waveform at 6 kHz.
Then I am using the "TotalSampPerChannelGenerated" property to monitor how many waveforms have been output.
What is weird, is that it appears my running total will roll over. So it increments for X minutes ... and then roll over and restarts.
Can onyone out there confirm this? And do you have any ideas on how to work around this issue?
05-07-2012 10:25 AM
Since data is returned as a floating point number, I wouldn't expect to see roll over within minutes... What hardware are you using?
Dan
05-07-2012 10:40 AM
I'm using a USB-6366.
And my DO task is running for many hours.
So I I've noticed the roll over sometime around 24-72 hours. Haven't tested it very thoroughly, though. With a little effort, I could find out exactly when it happens, but then I'll have to starty my application and wait a number of days again for it to happen.
I think I will just have to do that, though.
05-07-2012 10:42 AM
I'll see if I can reproduce something similar here... I'm hoping that if I up the rate, I'll be able to see the behavior is less time.
Dan
05-07-2012 11:05 AM
Thanks!
I am doing the same thing here. I upped my output frequency to 50 kHz and the counter appears to stop at 61273783.
I'll try again to see if it is repeatable.
05-07-2012 11:07 AM
Hmmmm.... wait a minute.
I think something else is going on here. This may be a triggering bug in my code. I might be inadvertantly receiving a pause trigger.
05-07-2012 11:19 AM
I ran at 5 MHz, and rolled over at 4.29 G... This sounds like a u32 roll-over.
In the short term, you may want to work around this by adding n*2^32 (where n=number of roll overs) to the value returned by TotalSampPerChannelGenerated if you detect that 'TotalSampPerChannelGenerated' has decreased. I'll dig through our code and verify that what we're seeing is indeed a u32 roll-over. I've filed CAR 353282 to track the issue.
Dan
05-07-2012 11:36 AM
Check that... I was running on the wrong device (a PCIe X Series device). I'm re-running my test with the USB version now.
Dan
05-07-2012 01:14 PM
Thanks, McDan.
I have tried to isolate the code so that I could upload a simple example of this issue. But now I can't seem to reproduce it.
However, I am reproducing another strange issue which has been plaguing me. Perhaps the two issues are somehow related.
Because it is a different issue, I will create a new post here:
http://forums.ni.com/t5/LabVIEW/DO-task-randomly-stops-no-errors-generated/td-p/1980915
Any chance you could have a look at it for me?
05-07-2012 01:35 PM
OK. Also just reproduced the roll over issue.
This doesn't seem to be a big deal. I can implement a workaround in my code.