>     My application is a digital tunner for musical instruments. My idea is
> to get the sound (or body vibrations) of the instrument and filter the
> harmonics. Let's say I'll want to tune an A (440Hz), so I'll make a very
> sharp filter at about 660Hz to trash the harmonics and count how many
cicles
> (clipped) the PIC seens in a given time to calculate the frequency and
show
> the user what note the instrumment is playind and how much sharp or flat
> this note is.
>
>     I think a DSP would be more inteligent than a PIC with external
filters,
> but I know nothing about designing with DSP and programming it, and have
no
> time to study it, as I have urgency with this project. :*(
>
>     Can you tell me more about how a DSP could make it?

That's a big question.  Programming a DSP is just like programming any other
microcontroller.  What distiguishes a DSP is usually instructions optimized
for doing convolutions.  This includes multiply-accumulates with the
associated address and counter logic so that one MACC can be done every
cycle.

If you're asking how to implement a digital filter, then you need to read up
on the theory.  It is not something easily answered in a few paragraphs.
Often with DSPs you transform the problem from frequency space to time
space.  So instead of doing a fourier transform, messing with the
frequencies, then doing the inverse fourier transform, you do the whole
thing in one convolution.  I'm sure there are lots of references about the
theory and implementation of digital filters you can look this up in.

If you need to get this done NOW, then you probably want to chose a
different approach or get someone familiar with this stuff to do the filter
part.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olin@embedinc.com, http://www.embedinc.com

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