[Dspforum] demodulator performance/frame synchronization

[Joseph Haber]

Mike,

Don't make any presumptions that a start falls on an "8" boundry -- in fact,
that concept doesn't exist until a start notification is found.

My first instinct is that EDMA makes this more complicated than you want --
you would have to be careful about processing across two sequential
"blocks", which seems like a pain to me.

Joseph

On Sun, Nov 16, 2008 at 4:39 PM, michael norris <mnorris at gmail.com> wrote:

> Instructors/students,
>
> Can we assume that a frame begins on an 8 (f_sample/f_symbol) sample
> boundary? In the general case, I don't think we can. If we can't, then it
> seems we need to compute an 8-point FFT per sample in order to synch the
> frame.
>
> Once we've synched on the frame, we could then compute the FFT once per 8
> samples. Then we would benefit from interleaving the sampling and
> computation with EDMA. But if our computation time must already be under one
> sampling time, then what benefit is there to implementing EDMA with this
> lab?
>
> (Maybe it prevent us from missing data during the printf() call. But do we
> care about this?)
>
> Could someone add a little more about detecting the frame boundary?
> Assuming we are sampling once-at-a-time to do the synchronization, where in
> the start bit's 8 samples do we fall? Are we one past the half-way sample,
> i.e. sample 5/8?
>
> We should have plenty of time to do our 8-point FFT with this board. I'm
> just curious where EDMA could benefit us here.
>
> Thanks,
> -Michael
>
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