DSA Input buffer overwritte​n error

Question

Hi All,
i am using 5 PXI 4472 and one FPGA 7833R. I need to perform continuous acquisition on all 40 DSA and 8 FPGA channels at maximum of 51.2 KiloSamples/second and 102400 Samples/block
In my code i am having a while loop which will acquire dsa and FPGA data and write to file. When i consider 51.2 Kilo samples and 102400 Samples/block, the overall while loop delay is between 2000 to 2100 milli seconds. Meaning the file write and other calculations are getting compelted within 100 mseconds. i have assigned the buffer size of 1 Msamples/channels for DSA.
I believe that even if the PC RAM size is greater, DSA allows only 1Msamples/channel buffer to allocate.
I have also assigned 1.7 MB for FPGA DMA transfer host memory.
When i acquire data simultanelously from FPGA and DSA in a single while loop, the acquisition is happening fine some 15 minutes after which DSA is giving DAQ channels overwritten error.
But when i bypass FPGA acquisition, there is no daq error generated and acquisition is happening fine.
i am have upgraded LV to 8.0.1
Please share thoughts and experiences to get this solved.
Thanks,
Sudha

Answer 1

The first thing I would try would be to update your RIO version to RIO 2.0.1.
http://digital.ni.com/softlib.nsf/websearch/12E9CA​0820A192F08625714F005A8B0C?opendocument&node=13206​...
Note this is an update to RIO 2.0 not a full RIO installation.  Also note that this is not RIO 2.0.2.  I do not think you need RIO 2.0.2.
Reasoning:  Reading data from the FPGA DMA channel is a blocking method when using RIO 2.0.  That means it will consume 100% of the CPU while trying to get the data.  This is obviously fast, but can starve other high priority operations like reading other DAQ channels.  RIO 2.0.1 allows the Read to sleep while rating for the data to arrive.
This may not entirely solve your problem, but it is a start and the update should definitely help a little.
Regards,
Joseph D.
National Instruments