As a follow up to this question: How to sample audio at Nyquist frequency with MSP430F5438?
What type of circuit would I use to generate something that a microcontroller could use to determine the max frequency of an input? I was thinking it would preferably provide a voltage that is lineally related to the frequency.
The information provided by the frequency detector could then be used by the microcontroller to know what frequency it needed to be sampled at.
Is there any ICs that do this? or any circuit that will do this?