Re: TWO PXI 6070E have problems to adquire at high speed

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On Friday 28 November 2003 07:05 am, David wrote:
> Hi all,
>
> We have in our system REDHAT 9, kernel 2.4.22 vanila, patch adeos, RTAI
> 24.1.12, and the latest CVS comedi version. We are testing comedi
> adquiring at 1.25Ms/s. If we use only one PXI 6070E card we have not any
> problem to adquire at that speed, but when we use two cards (PXI 6070E)
> the adquisition of one of the cards is stopped (both cards at 1.25Ms/s).
> The other card continues working perfectly.
>
> We think that comedi moves data to their buffer when one card has a
> number of samples greater than PAGE_SIZE (4096) ¿is it right?
>
> If that is true, we think too, that increasing the number of samples to
> read at a time (for example 16K instead of 4K) we will  improve the
> system, and adquiring from two cards at 1.25Ms/s each, will work.
> ¿what do you think about that idea?

It seems unlikely to me that the board's hardware fifos are overflowing, 
since they are being emptied by their pci chips using dma.  How big a 
memory buffer are you telling comedi to use (see the --read-buffer option 
of comedi_config)?

- -- 
Frank

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Received on 2003-11-28Z23:01:43