Your first step must be to determine what, exactly, "isn't working";

Once you know what isn't working, then you can find out why it isn't working;

Once you know what isn't working and why, then you can fix it!

This process is known as debugging.

See: http://www.8052.com/forum/read.phtml?id=118587


You have several distinct functions here:

measure the frequencies;

some calculation;

display on an LCD.

You need to isolate each one and make sure it's working before adding the next.

I recommend starting with the LCD - as that will give you a way to display results of the other steps.

As others have suggested, for the frequency measurement, start with just one. I would also suggest that you start with a known square-wave generator before using the actual sensors.

Have you tried it in a Simulator?