FFT on Arduino

I have a project in which i will have to show heart beat in bits per minute. I am using a microphone to get the periodic signal of my heartbeat. But I am unable to convert the signal into frequncy domain. I dont understand the code. Can anyone urgently help me? Please?

For informed help, please read and follow the directions in the "How to use this forum" post.

Have a look at any Arduino heartbeat project online. None of them use FFT. Unless you have unusual requirements i expect that you don't need FFT.

Also, the problem is in the code you didn't post.