Simple example for programming PCI-6221 under Matlab.

[Jens_DE]

Hi!

I ran into what seems a similar problem.
I am programming a 6221-M under Matlab, using the C-libraries. So excuse the strange syntax.

I try to sample AI channels and one counter, using the BNC 2120 device.
I have two tasks at the moment, supposed to run on the same device. Task(h)1 is AI and task(h)ctr is the Counter.
for each analog sample, I want to read out the current counter.
The counter works, I was able to test it in MAX. It is connected to PFI8.

Both tasks should start when an external Trigger on PFI0 occurs.

Here's my code (declarations omitted for clarity - hopefully):
[a,b,taskh1] = calllib('myni','DAQmxCreateTask',taskname1,taskh1);
[a,b,taskhctr] = calllib('myni','DAQmxCreateTask',taskname4,taskhctr)
[a,b,c,d] = calllib('myni','DAQmxCreateAIVoltageChan',uint32(taskh1),taskchans1,'',-1,-10,10,DAQmx_Val_Volts,'');
[a,b,c]=calllib('myni','DAQmxCreateCICountEdgesChan',taskhctr,'Dev1/Ctr0','',DAQmx_Val_Rising , 0,DAQmx_Val_CountUp )
[a,b]=calllib('myni','DAQmxCfgSampClkTiming',taskh1,'',fsample,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,nsample)
[a,b]=calllib('myni','DAQmxCfgSampClkTiming',taskhctr,'/Dev1/ai/SampleClock',fsample,DAQmx_Val_Rising,DAQmx_Val_FiniteSamps,nsample)
[a,b]=calllib('myni','DAQmxCfgDigEdgeStartTrig',taskh1,'/Dev1/PFI0',DAQmx_Val_Rising );
[a,b]=calllib('myni','DAQmxCfgDigEdgeStartTrig',taskhctr,'/Dev1/ai/StartTrigger',DAQmx_Val_Rising )
This last line gives me an
-200452 = DAQmxErrorAttributeNotSupportedInTaskContext = Specified property is not supported by the device or is not applicable to the task.
It does not matter which terminal I specify, even 'nonsense' will give the same error.

I haven't tried this duplicate count prevention, because my problem seems to be more basic than duplicate counts - it does not count at all.

Any ideas? Do digital/counter channels need another set-up function?
I had a serious look at the "Finite Counter Input Programming Flowchart" in the C reference, but couldn't make much use of it 😕

Regards
Jens

[reddog]

I think this is really an artifact of how the data is transferred in the driver. In order to optimize throughput across the PCI bus, the DAQmx driver will read 8 bit digital samples from the device until it can DMA 32 bits of data to host memory. While this does introduce some latency, it greatly increases overall throughput across the PCI bus for higher speed acquisitions.

[reddog]

Sorry, that last post was in response to Daytona Ed's question (response 9).

[Kapp]

Hi Jens,
sorry for contacting you directly. But this seems to be the best way to get my matlab code running.
The only and pretty simple thing I have to do is acquiring analog data using BNC 2110.
Could you please send a piece of code containing the required steps (how to load which library etc.).
Your help will be appreciated.
Many thanks in advance
Andreas

[Jens_DE]

Hi Andreas!

Sorry for the delay!
I started a separate thread for using DAQmx with Matlab.
I hope I have a download ready by tomorrow!
So long:
http://forums.ni.com/ni/board/message?board.id=250&message.id=10167

Jens