On Thu, 12 Apr 2001, Andrew Warren wrote:

> Dale Botkin <PICLIST@MITVMA.MIT.EDU> wrote:
>
> > >   FILT <-- FILT*(1-F) + NEW*F
> >
> > Man, here is where I run into a wall.  I am totally unfamiliar
> > with digital filtering techniques.  What is F?  Is it the inverse
> > of the number of samples added to the accumulator?  I keep thinking
> > I can see how this works, but then I plug it into Excel and it
> > doesn't work. Should've gone for that engineering degree.
>
> Dale:
>
> The people who've been posting on this subject presumably have
> engineering degrees, yet they haven't been able to explain the filter
> clearly enough for you to understand.  Don't wish for a degree; it'll
> only make you part of the problem.
>
> Here's how the filter works:

<snip>

Bravo!

> In fact, if you choose a window size of 256, the division completely
> DISAPPEARS; it doesn't take ANY code to perform.  To see the code
> required to perform this filtering algorithm with a window size of
> 256 (as I recall, it required less than 20 words of non-looped code),
> search the PICLIST archives; I posted it a few months ago.

If you want another implementation then check out:

http://www.dattalo.com/technical/software/pic/twist.asm


Scott

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