Kerry Wentworth wrote:
>>   FILT <-- FILT + FF(NEW - FILT)
>>
>> where FILT is the low pass filter being updated with input value NEW
>> each iteration.  FF is the "filter fraction".  FF =3D 1 is just a pass
>> thru filter, and FF =3D 0 is a infinitely heavy filter.  Useful values
>> are obviously in between.  In a small system with limited math
>> capabilities, you often arrange FF =3D 1/(2**N), so that the multiply
>> by FF becomes a right shift by N.
>
> I would normally implement such a filter as:
>
> Total =3D Total + New - Filt
> Filt =3D (Total+1) / Factor

I'm not sure what exactly that results in, but it's not a single pole low
pass filter, otherwise known as a exponential decay.  The simple case of a
unit step input with N=3D1 proves that easily enough.  Your filter jumps to=
 1
in the first iteration, then stays there.  It also requires more computatio=
n
and more persistant state, so it's not clear what the advantage is.


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