I got Fast Fourier Transform core in my design. Seems to work pretty well. The output is in Natural order, using 256 samples. The question is, how to represent output ? How do I match output (spikes in the frequency domain) to a specific frequency ?
E.G. I got spike at 32nd position (out of 256) in the frequency spectrum (FFT output), and the FFT core runs at 40 MHz aiming at 1 MSPS. What is the identified frequency ?
