strange behaviour in multiple AO generation

[Dany27]

Hello,

I am doing signal generation on the 2 AO channels of my pci-6071E card.
I configured a DAQmx task for it.
The purpose is to generate simultaneously and continously on the two channels, respectivly two arrays of 6000 pts.
So I build up a 12000 pts array with the two previous ones.

It works fine most of the time except approximatly each 30 times. There, the two signals are inverted !!
I verify the building of my 12000 pts array, but the first 6000pts for the first channel are at the beginning and the second array for the second channel at the end.

How can this be possible, is there a bug?

Quotted from my code:

Configuration:
    DAQmxErrChk (DAQmxCreateTask("",taskHandle));
    DAQmxErrChk (DAQmxCreateAOVoltageChan (*taskHandle, chan, "", min, max,
                                           DAQmx_Val_Volts, NULL));
    DAQmxErrChk (DAQmxCfgSampClkTiming(*taskHandle,"",rate,DAQmx_Val_Rising,DAQmx_Val_ContSamps,1000));
where chan="Dev1/ao0:1"
           rate=200000

Writting:
    DAQmxWriteAnalogF64(taskHandle,bufferSize,0,10.0,DAQmx_Val_GroupByChannel,data,&written,NULL);
where bufferSize=6000
           data=float64[12000]

After that i only start and stop the task

Is someone got tips or clues to solve my problem?

Yop!
DanY      

[ChristopheS.]

Hello Dany,

It's possible that you join you project (or file) in this post. I want see the code *.c, and make test in my computer.

Thanks,

Message Edité par Christophe S. le 01-12-2006 04:52 PM

[Dany27]

I extract from my code the relative functions and try to make a usable file. I've also commented some elements that are not directly involved in the signal generation (mostly a acquisition task using that signal as a external clock).

Thanks
Yop!
DanY

[ChristopheS.]

Have you try with an example, if we have the same problem ? (the link below has example to generate in two channels)

And try to modify an example that can generate your array.

See the link below, they can help you.

http://forums.ni.com/ni/board/message?board.id=250&message.id=13095&requireLogin=False

http://forums.ni.com/ni/board/message?board.id=180&message.id=13388&requireLogin=False

http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=E863083C10683BFFE034080020E74861&p_...

It's possible to have a screenshot (or image) with the problem ?

What is the reference of your NI board ?

It's possible to have an simple example (or project) for reproduce the problem ?

Just with an array and generation on the two channel.

Regards,

[Dany27]

I tried the example of your third link on my card:
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=E863083C10683BFFE034080020E74861&p_...

And it happened again with the following configuration that generate a signal similar to mine.

Channels:  Dev1/ao0:1
Amplitude 5V
Frequency 150 for the first channel
                     15 for the second one
Timing 100 000 or 200 000

It seems to happen more often when you start the task after waiting a minutes (i.e. after doing some settings) but also when starting and stopping the task very quickly.

I've monitored it on an oscilloscope, I connected the two AO respectivly to the two oscilloscope channel inputs and the AOgnd on the two channel gnd.

The reference of my 6071E NI-board is 184411F-01

Thanks
Yop!
DanY

[ChristopheS.]

Hello Dany,

Have you try to uninstall you NI-DAQ driver, and re-install the new version ?

If you want you can call me to National Instrument France with this Service Request : 317222.

thanks,

Christophe

[Dany27]

It works fine with the new NiDaq 8.0

Thanks for your help

Yop!
DanY