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Pot Controlling a Multiplexer

Question asked by ByronS on Jun 19, 2013
Latest reply on Jun 20, 2013 by BrettG

Another part of my application requires the use of a Pot fed into an A/D input so that it can control the audio path selected by a mux. The idea is to select 1 of several different compressors with different noise gates, but for now to make testing easier, the compressors have been replaced by sinewave generators as the signal source so the path selection is easier to see on the scope.

The reason I'm trying to use the tolerance analyzers at the front end is so that I can have a larger portion of the Pot rotation selecting a given signal path. By this I mean the first 1/4 rotation will select one audio path, the second 1/4 rotation the next, etc.

I can get the A/D input to work fine with the tolerance analyzers, but I don't seem to be setting up the numbers properly in the lookup table. I've read numerous posts and understand that the lookup table needs values in 5.23 format. I believe I understand the number format coming out of the Buffers is in 28.0 format, so I'm applying the formula of N(5,23) = N(28.0) x 2^-23 and putting those into the table. The index selectable mux is still only choosing the first audio path so I always end up with a 1KHz tone output.

 

There are likely many ways that are better to set this up than this, so I'd really appreciate other suggestions on the method. What's wrong with my lookup table numbers?

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