I guess it's old news that you can get these HB100 doppler radar modules quite cheap, like under $7 on ebay. In case you were looking for cool things to do with your FFT function, I think this is one of them (calculating speed of cars or other things, from the frequency peak):
https://www.eevblog.com/forum/proje...r-module-for-car-speed/msg1263576/#msg1263576
It really benefits from the FFT because if you just do a dumb frequency counter, it will likely have a problem with low frequency noise interfering with the real signal.
https://www.eevblog.com/forum/proje...r-module-for-car-speed/msg1263576/#msg1263576
It really benefits from the FFT because if you just do a dumb frequency counter, it will likely have a problem with low frequency noise interfering with the real signal.