PDA Error code: -200714

[Dennis Francek]

Hi

Im developing a program for a PDA to collect Heart Sounds where im using a NI USB-9215A BNC to collect the data. I need to collect the data continuesly and for instant display on a graph. When i start the vi i get data in for a few seconds before i receive the above error.

I think it has something to do with some internal buffers getting filled in the daq device before the PDA can retrieve it or maybe my program is structured the wrong way. It works great on my desktop pc though.

Im using a Juniper Archer Field pc which was recommended by National Instruments. 

Im submitting my vi and im looking forward to some feedback on this problem.

/Dennis

[Morini]

Hi Dennis,

You are seeing Error -200714 because the limitation of the PDA processing power is not able to keep up with the sampling rate in your application. The Filter and Sound functions are requiring alots of processing power. Because you have a single loop structure where the DAQmx read is running on a predefined samplingrate, you will get this error if the rest of the code in the loop can't "keep up":

"

Error -200714 occurred at DAQmx Read.vi
   Possible reason(s):
   Acquisition has stopped because the driver could not transfer the data from the device to the computer memory fast enough. This was  caused by computer system limitations.
   Reduce your sample clock rate, the number of channels in the task, or the number of programs your computer is executing concurrently.

"

You can test this by removing/disabling the Filter and Sound vi's in the loop.

You have a couple of options:

Try to reduce the sample rate if possible.

Try to reduce the PDA processor load if possible.

Depends on your application requirement, you might not need ALL the samples to output the sound(I presume that you want all samples on your Waveform Chart):

Try to move the sound output functions to a separate parallel loop sturcture.

Hope this helps

Thanks!

[Dennis Francek]

I tried doing the suggested and i removed all vi's but the daqmx base.

It didnt work at all. So i tried changing the chart to a graph. That works!

But i want to display the samples at once, not each 4 seconds. By doing that the user cant interact for those 4 seconds and i cant see chart history at a large period of time like 8 seconds.

So i think theres a problem with the way the Chart works on PDA's. The first time the chart shows the samples it works fine. But when the chart is filled up with plots it then needs to update the screen. When that happens the speed goes very low and a few moments later i get the error from my first post and the program crashes.

I found this in the known issues for Mobile Module:

Charts draw incorrectly when the number of points on screen exceeds the chart history length.

Workaround—Change the chart history length to accommodate the number of points drawn on the chart before it scrolls.

I tried changing the chart history to 10k and even 100k samples but i still get the same error at the same point of time.