So, this might be a good time to recap.

Method 1:

FILT <-- FILT + FF(NEW - FILT)

Requires:  2 add/subtracts 1 multiply/divide/shift


Method 2:

Total =3D Total + New - Filt
Filt =3D Total / Factor

Requires: 2 add/subtracts 1 multiply/divide/shift

Rounding instead of truncating requires 1 extra add in each case.

The difference is in the format of the answer, binary vs. 10.6, and one ext=
ra variable in method 2 which holds the filtered value in 10 bit binary for=
mat.

Is that a fair assessment?

Kerry



Olin Lathrop wrote:
> Kerry Wentworth wrote:
>  =20
>> My Filt is the Total (or your Filt) right justified and truncated (or
>> rounded) to 10 bits, to give a filtered A/D between 0 and 1023.
>>    =20
>
> Yes.
>
>  =20
>> This step is optional, if one wanted the 14 bit number, one could
>> skip the conversion.
>>    =20
>
> No, not with your algorithm, since it requires your FILT in a previous st=
ep.
>
> It is optional in the normal method that I described.  You can convert to
> the original integer scale when you want, but are not forced to do so eac=
h
> iteration.  More likely, you adjust the scale factors in the rest of the
> system so no conversion is ever required.  Usually the A/D values are in
> some arbitrary scale, so having values in that scale times 2**N is no
> different in that it's just as arbitrary.
>
>  =20
>> And your FF(NEW - FILT) is really (NEW - FILT) / FF.
>> Is this correct?
>>    =20
>
> Clearly not if FF can take on values other than 1, which of course it can=
..
> As I said before, useful values for FF are between 0 and 1.  For easy
> implementation on small systems, FF =3D 2**-N since the multiply by FF th=
en
> becomes a right shift by N.
>
>
> ********************************************************************
> Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
> (978) 742-9014.  Gold level PIC consultants since 2000.
>  =20



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