>hello all,
>
>I work with EZ-Kit Lite 21161N and AD 1836, sample frequency in 48k ! 
how
>can I down the sample frequency to 8k ??
>
>I know, I need decimate... but I don't know how !!!

yes... now I think, I understood, my problem is, I need more time to
process the algorithm between one sample and other... well, 48k of sample
frequency is too much to me... so, an solution is downsample to 8k...

so I need that my processor run my algorithm before read the next
sample... and with 8k it is ok....

thank's... I'll read the articles and see what can I do !!!!

I think, a possibilite is, when the interrupt call to read the next sample
(ad1836), I put the condition (if) and a counter to read the sample six by
six... 

what do you think ???  there is a overhead but I've more time between one
sample and other...

henrique

>
>somebody know a article, book or something ??
>
>thank's
>
>Henrique
>

hbarcellos wrote:
> hello all,
> 
> I work with EZ-Kit Lite 21161N and AD 1836, sample frequency in 48k !  how
> can I down the sample frequency to 8k ??
> I know, I need decimate... but I don't know how !!!
> somebody know a article, book or something ??
> 

I like this one:
http://www.dspguru.com/info/faqs/mrfaq.htm

-- 
Jim Thomas            Principal Applications Engineer  Bittware, Inc
jthomas@bittware.com  http://www.bittware.com    (603) 226-0404 x536
Being a good example is hard.  I'm trying to serve as a horrible
warning instead. - Brian Crane

hbarcellos wrote:

> hello all,
> 
> I work with EZ-Kit Lite 21161N and AD 1836, sample frequency in 48k !  how
> can I down the sample frequency to 8k ??

The decimation is a minor technical problem.
The real question is why do you have to decimate.

> I know, I need decimate... but I don't know how !!!

Eh? Drop the clock rate on the codec then.

> somebody know a article, book or something ??

L. Rabiner "Multirate Signal Processing"


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

hbarcellos wrote:
> hello all,
> 
> I work with EZ-Kit Lite 21161N and AD 1836, sample frequency in 48k !  how
> can I down the sample frequency to 8k ??
> 
> I know, I need decimate... but I don't know how !!!
> 
> somebody know a article, book or something ??
> 
_Just_ decimation means taking one of every N samples -- in your case 
you'd need every 6th.

Do you need to anti-alias filter as well?  In that case you run your 
anti-alias filter (usually a FIR filter) over whatever span of samples 
it needs, at 1/6th the 48kHz sampling rate.

Get a copy of Rick Lyons' "Understanding Digital Signal Processing", see 
if it helps out.  In the mean time, here's a bit about sampling, which 
also applies to decimation if you hold your mouth right: 
http://www.wescottdesign.com/articles/Sampling/sampling.html.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

"hbarcellos" <henrique_barcellos@hotmail.com> writes:

> hello all,
>
> I work with EZ-Kit Lite 21161N and AD 1836, sample frequency in 48k !  how
> can I down the sample frequency to 8k ??
>
> I know, I need decimate... but I don't know how !!!
>
> somebody know a article, book or something ??

@BOOK{lyonsnew,
  title = "{Understanding Digital Signal Processing}",
  edition = "Second",
  author = "{Richard~G.~Lyons}",
  publisher = "Prentice Hall",
  year = "2004"}
@BOOK{mitra,
  title = "{Digital Signal Processing: A Computer-Based Approach}",
  author = "Sanjit~K.~Mitra",
  publisher = "McGraw-Hill",
  edition = "second",
  year = "2001"}

>
> thank's
>
> Henrique

-- 
%  Randy Yates                  % "Rollin' and riding and slippin' and
%% Fuquay-Varina, NC            %  sliding, it's magic."
%%% 919-577-9882                %  
%%%% <yates@ieee.org>           % 'Living' Thing', *A New World Record*, ELO
http://www.digitalsignallabs.com

hello all,

I work with EZ-Kit Lite 21161N and AD 1836, sample frequency in 48k !  how
can I down the sample frequency to 8k ??

I know, I need decimate... but I don't know how !!!

somebody know a article, book or something ??

thank's

Henrique