Hello Dear Fellows!

I urgently need a frequency counter program that can count form 1 HZ to 50kHz.
I am working on the technique of if the controller sees the high edge then
Start the counter and stops on the next high edge. Now form this method i have the time period.


How can i convert this to frequency and rpm

Thanks, if any one has made the frequecny counter or 5000rpm meter plz give me the url