> May need to cast an operation to a larger storage variable

If I'm right in assuming that there's some asynchronicity between the
wave edges and when the PIC recognises them (ie a small portion
of each of the many waves in the sample is lost), then larger "variable"
could be an external divider

A /512 (or whatever sample size Fred decides on) external counter
would be synchronous with the edge events and not accumulate the
small errors as the PIC does. The only error, at the PIC, would be
the part-cycle one at the time of measurement

wbr, Joe
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