Hi, pete,
It worked! Thank you.
When I tried to to have A =1 from "k = Asin(23.14159 * 100 * t / 400 )", every bin is zero. When I used large A,I was able to see much larger numbers in the bins where the frequency closest to. I still have a lot of other numbers in other bins. Is that normal to FFT?
I can set a limit and filter out these numbers, but I wanna make sure I'm using FFT correctly.