Finally got around to implementing/trying some proportional filtering [ 
N=N+(N-L)*K ] in one of my pieces of PIC code (which is essentially a 
frequency counter).  This thing is sweet!  I've experimented with K=1/4, 1/2, 
and 3/4.  For my app, 3/4 works well (but I still have a bit of averaging in 
there still, since I'm experimenting with combinations of averaging and 
proportional filtering).

BTW, I chose these constants since they made for some simple assembly code.

Curious about one thing though -- anyone have a correlation or calculation to 
compare software proportional filtering to an RC filter?  Or asked another 
way -- how do I determine the equivalent hardware filter time-constant for a 
proportional software filter?  I'm sure the update rate of the calculations 
will be a factor here.

I don't really need this for anything specific, just think it will be an 
interesting tidbit of info.

Cheers,
-Neil.


-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist