This is an agriculture application. I am going to measure seed population. The seed rate (population) is dictated by two variables; seed plate count and rpm. Seed plate count is how many seeds are dropped per revolution. This can vary from 12 to 120 seeds revolution and the rpm can vary from 12 to 80 rpm.

So a minimum frequency is 2.4hz and maximum is 160hz.

There are a couple things to keep in mind. Sometimes there is a 'skip' this is when a seed doesn't get into the seed plate and consequently not dropped into the ground. I need to detect the skips. I also need to be able to report population atleast every tenth of a second when the population frequency allows it.

There are a couple of ag manufacturers that already do this. I just need to figure out how. The one 'Seed monitor' I have on my test bench is completely potted so I can't take it apart and learn anything.

I am thinking I use smaller slave chips with a DtoA and CCP pin. The CCP measures the frequency and then I give an analogue out. The master then measures the 0-5v signal to record the population.

Another thought is using a PIC with many CCP pins but I just don't know how that will work due to the leading edge of each input not being aligned.