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  #1  
Old 12-23-2015, 11:29 PM
shirsch shirsch is offline
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Default Logarithmic response to analog input?

I have a feature request: Would it be possible for the MIDI CPU to produce a log response to input voltage change in software? Doesn't have to be instrumentation grade. A lookup table and/or simple-minded interpolation is close enough.

My immediate issue is the need to piggyback analog control on the mag pickup volume pot in my guitar. Most CC analog controls in my Roland / Boss products expect a linear voltage ramp. Since it's relatively easy to get ganged audio-taper pots a log function would be handy here!

I briefly looked into building an op amp based log amplifier circuit, but it starts getting complex rather quickly and requires calibration. Better done in software if at all possible.

Bump: Hello? Is this on?

Update: I found a rather elusive bit of PIC assembly code for fast 8-bit logarithms. Let me know if you want a copy?

Last edited by shirsch; 12-28-2015 at 06:55 PM. Reason: No response - not seen?
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  #2  
Old 01-06-2016, 12:00 PM
shirsch shirsch is offline
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Bump... Would appreciate some sort of response to my original post - thanks.
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  #3  
Old 01-08-2016, 02:33 AM
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Synthetech Synthetech is offline
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Hi,

sorry for the lack of response.

I doubt any changes to the MIDI CPU's firmware can be done to meet your needs.
It would require the designer/author, John S., to do it and I think he may be deep into other projects right now.


I'd suggest PM'ing him and ask him directly.

this link may take you to his profile, just click "Send Message" below his name to send off a PM

http://forum.highlyliquid.com/member.php?u=2


another thought is to check into using an Arduino and the MIDI Library to custom build a device to translate your voltage controls for you.. something you'd have to get support for elsewhere, I'm afraid.

Last edited by Synthetech; 01-08-2016 at 03:01 AM.
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