> On Tue, 10 Aug 2010 08:19:32 -0700 (PDT), "kris duff" said:
>> Hello,
>>
>> My colleage told me about a smoothing/lpf formula which is :
>>
>> a(n) =3D {a(n-1) * param + ADC} / {param + 1}
>>
>> which
>> ADC is the signal from adc
>> a(n-1)=C2=A0 is the result of the last call to this formula
>> the param is the part I don't understand.
>>
>> Is there anybody knows where this formula comes from ?
>>
>> it seems to work well for smoothing, but I want to tweek the param (
>> which is certainly for the bandwith )

I have used this with param=3D0 (just use current ADC) and with param=3D1
(mean of old value plus current adc). The param determines how much of old
values you're using. It's interesting to look at a step response to this
LPF. If the ADC value goes from 1 to 0 in one sample, the output goes 1,
0.5, 0.25, 0.125, etc. Note that it's a linear decline while a single pole
RC would be an exponential decline.

Harold




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