> From: KŸbek Tony 
> 
> Thanks to all who responded, I will whip up Matlab
> and se what effect will come of the FIR vs. IIR filters.
> If it has the filtering/freq responce(damping) I need
> then one could not comlain about ram usage :-) .

A couple of things to take into account with digital filters:  While FIR
filters are more memory and computationally intensive, they do have one
great advantage, they are universally stable- no matter what, if you have a
filter that is N taps long, no input more than N+1 delays ago will affect
the output.  IIR (*Infinite* Impulse Response) filters have no such bound.
IIR filters can have stability problems (meaning that it may oscillate after
an input, possibly out of control).  In a system like a PIC where you are
most likely to use fixed point math, you must be much more careful in
implementing the filter and studying the effects of quantization, sampling
rate, and a limited dynamic range on your filter.  Doing your analysis in
Matlab can give you a false sense of security, unless you build these things
into your model.

Bang for the byte- IIR is best, but sometimes, an IIR will misfire.

Matt Bennett