[sdiy] Digital filtering of pot input

Andrew Simper andy at cytomic.com
Sat Dec 3 10:40:43 CET 2016


Hi Matthias,


On 3 December 2016 at 01:23, Matthias Puech <matthias.puech at gmail.com> wrote:
>
> [Oops, I realize I had not CCd this reply to the list]
>
> This is actually what I already do (boxcar on 32 values -> hysteresis -> boxcar and IIR again to smooth out the staircaise), but it's conceptually ugly and you can still hear a weird staircase when turning the pot delicately, even with a low threshold.
>

If you have enough DSP to throw at multiple boxcar filters and an IIR
you may be interested in a dynamic 2 pole low pass filtering approach
I've designed which gives these kinds of results:

www.cytomic.com/files/dsp/dynamic-smooting.png


It takes 2 multiples, 6 additions, 3 bit shifts and an absolute value
for fixed point, or 5 multiplies, 6 additions and an absolute value
for float. Please let me know if this sort of algorithm may be
appropriate.

All the best,

Andrew


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