Forums

EDMA reset

Started by silvera_tristan September 7, 2004
Hi all,
I'm using DSKC6713 and I want the DSP to search for a certain
sequence of samples in a buffer, received from the McBSP. As soon as
this sequence is found, I want the element count of that channel to
start from zero (i.e, some kind of reset to the EDMA channel). Is
that possible, and if so, what register should I write to to make
this happen?
My EDMA transfer is element sync'd, and my events are McBSP receive.
Thanks,
Offir.




Offir-

> I'm using DSKC6713 and I want the DSP to search for a certain
> sequence of samples in a buffer, received from the McBSP. As soon as
> this sequence is found, I want the element count of that channel to
> start from zero (i.e, some kind of reset to the EDMA channel). Is
> that possible, and if so, what register should I write to to make
> this happen?

That does not sound like a good idea. You will be messing at the chip level
with DMA
transfers in "mid-stream"; if the data rate is high, you could miss/overwrite
samples
or otherwise cause some glitch.

Why not just note the sample offset at the time the sync sequence is located?
For
each buffer after that point, you take some of the current buffer and some of
the
previous, and based on the offset, and process as needed.

-Jeff




Offir-

On Tue, 07 Sep 2004 14:12:21 -0500, Jeff Brower <> wrote:
>
> Offir-
>
> > I'm using DSKC6713 and I want the DSP to search for a certain
> > sequence of samples in a buffer, received from the McBSP. As soon as
> > this sequence is found, I want the element count of that channel to
> > start from zero (i.e, some kind of reset to the EDMA channel). Is
> > that possible, and if so, what register should I write to to make
> > this happen?
>
> That does not sound like a good idea. You will be messing at the chip level
with DMA
> transfers in "mid-stream"; if the data rate is high, you could miss/overwrite
samples
> or otherwise cause some glitch.

Even I think that its not a good idea to meddle with the transfer when
its actually taking place.

But if your data rate is not that high and you have *enough time*
between subsequent samples then how about setting EDMA transfer for
just one sample and let it interrupt CPU after every sample and let
CPU deal with finding that sequence you are looking for.

I still think the method I have suggested doesnt make much sense since
the onus of processing and transferring data is back on CPU and kills
the meaning of EDMA . ( It mite be of some help in scenarios where ur
data is coming at vrey slow rate and hence CPU can utilize the time in
between samples to do other things)

Just a thoght
Tarang
>
> Why not just note the sample offset at the time the sync sequence is located?
For
> each buffer after that point, you take some of the current buffer and some of
the
> previous, and based on the offset, and process as needed.
>
> -Jeff

>
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