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Pot Tracking Speed
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MacroMachines



Joined: 12 Dec 2014
Posts: 70
Location: Detroit,MI

PostPosted: Mon Jul 11, 2016 1:39 am    Post subject: Reply with quote

You are correct, I was using a ramp from my micro controller dac and realized the derp that of course my upward movement is going to not show as much since the ramp is going up :/

Sometimes I wonder how I am even able to do this stuff at all haha
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MacroMachines



Joined: 12 Dec 2014
Posts: 70
Location: Detroit,MI

PostPosted: Tue Jul 12, 2016 2:10 am    Post subject: Reply with quote

donstavely wrote:

Code:

equ   potfilt   reg0
equ   fastpot reg1   

rdax   pot0, 1
rdfx   potfilt, 0.001    ; this is the shelving highpass filter
wrhx   potfilt, -0.75    ; it cuts lower freqs by factor of 4
rdax   fastpot, 0.75     ; this gives 4X recursive gain
wrax   fastpot, 1        ; to recover full range


If you want to make the control faster than 4X better, you just need to adjust the filter and gain coefficients.

I tested the algorithm by injecting a 1Hz square wave into the pot input to simulate instantaneous changes to the control. The normal pot output has a long (100ms) time constant. The fast control output is indeed 4X faster, and is still clean and filtered. I have a scope picture, but I can't directly attach it.



I am wondering the nature of the 100ms time constant, is this happening in the hardware? like an analog RC lowpass filter? I just wanted to try and figure it out to see if I can hone in on an optimal coefficient for the highness and also to use in my little modular simulator patch Im making in Audulus3
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frank



Joined: 19 Oct 2005
Posts: 972

PostPosted: Tue Jul 12, 2016 10:28 am    Post subject: Reply with quote

Yeah, it is a filter in the POT ADC. It was done so the POTs would have stable values even in an environment with vibration (i.e. a stage).
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