multiple channel data acquisition

[ajmal]

hi sir;

i want to get the voice data from 8 channels in 8 different buffers.The acquisition should be continious.Please tell how this will be possible using daqmx API's and what procedure should be followed.Also specify what API's should use.Please donot say the tradition answer  "see the National instruments examples etc.etc".Please tell complete sequence of API's.

 I have installed 7.4 version.

I want to acquire continue one minute data from 8 channels in 8 buffer after the one minute all the data of 8 buffer should be transfered to other 8 buffer and the continous acquistion should be contineoued. I m using DAQ6025E.

                        thanks

                                    ajmal

[AlanArmstead]

Hello ajmal,

As stated in this post, there is no DAQ function (Traditional NI-DAQ or NI-DAQmx) that will create 8 separate buffers for 8 individual channels.  As previously mentioned, you simply need to perform some array manipulation to break up the data array into 8 arrays.

-Alan A.

[ajmal]

hi dear sir;
thanks for reply  please tell how can i get the voice data from 8 channels in DAQMx 7.4.
As we use the api:
1.daqrate
2.scanseup
3.scan_start
please tell how i can get the data in DAQMx jut like using the above API in NI6.9.2 version.Because i want the same functionality as the above API's perfom.
                                                                   ajmal

[AlanArmstead]

Hello ajmal,

I'd be happy to point you in the right direction.  What programming language are you using?

-Alan A.

[ajmal]

thanks sir for reply

I m using Visual c++ please reply as soon as possible.bye

ajmal

[AlanArmstead]

Well, in NI-DAQmx, the function calls won't be exactly the same.  However, you can achieve the same functionality.  There are a bunch of great examples that install with NI-DAQmx.  For analog input, I would suggest looking here:  C:\Program Files\National Instruments\NI-DAQ\Examples\DAQmx ANSI C\Analog In\Measure Voltage.  You might want to check out the folder called "ContAcq-IntClk" for a continuous analog input example.  To acquire from multiple channels, you simply need to change the physical channel input from "Dev1/ai0" to something like "Dev1/ai0:7".  That will acquire data from channels 0 through 7.  Additionally, if you used "Dev1/ai0, Dev1/ai3, Dev1/ai5", that would acquire data from channels 0, 3, and 5.

-Alan A.

[pavanbabut]

Hi Alan,
Are you sure it is as simple as just changing the physical channel from ai0 to ai0:2 (if 0,1,2 are to be used) for multiple channel acquisition?? It seems pretty hard to come up with a buffer number which can run without errors and then comes the pain when we have to store and write the data into a file. I have a dual xeon processor system with 2GB of RAM, so I try to allocate as much memory as I want to store the data while acquiring, but still the program gives out error at the begining itself. Here is the code that I am using. It would be great if you can check it out for any errors. I started out from 1kS buffer size all the way upto 1MS buffer size. Untill 10kS it is giving status error code : -200279 and from there after the program just crashes. I tried the program with and without saving data while acquiring.
thanks,
-Pavan

[AlanArmstead]

That error indicates that the driver-level buffer is overflowing (not application level, where you currently allocating memory).  You can increase the size of the buffer DAQmx uses with the DAQmxCfgInputBuffer function.  Could you give this a try?

Oh, and I assuming you are using a 10MS/s Simultaneous Sampling device, right?  6115?

-Alan A.

Message Edited by Alan [DE] on 05-16-2006 06:42 PM

[pavanbabut]

Hi Alan,
Thanks for your reply. Yep I am using PCI-6115 for continuous and simultaneous sampling of 3 AI at 10MS/s. I can acquire 1AI-2DI with no errors, but for 3AI it's giving out above errors. I will try the function that you mentioned above and let you know.
thanks,
-Pavan.

[pavanbabut]

Hi Alan,
Its not working using that function either. Can you try this program at your end and see if you can record data successfully from 3 AI at 10MS/s??
Thanks,
-Pavan