Posted on March 27, 2014 at 21:36Dear Gentleman,
In your application case, our fast A/Ds are 12-bits, so using Q15 fixed point FFT is enough to process your data. You do not need Q31 or Floating point unit, the FFT you can use might be FFT 512 points in real format not complex.
But here I can give you some
relative data
for FFT-1024 points and FFT-256 points but “complex� not real using CMSIS DSP library we provide on-line. To have an overview in average for only the Core comparison between M0 (STM32F0), M0+ (STM32L0), M3 ( STM32F1,F2, L1) and M4 ( STM32F4,F3), the units are in CPU cycles and using 0 wait-state Flash execution
.
so you can compute at each selected frequency.
1024-FFT (Complex in Q15 Format)
Cortex-M0 : 855 733 cycles
Cortex-M0+ : 664 531 cycles
Cortex-M3 : 204 244 cycles
Cortex-M4 : 89 839 cycles
256-FFT (Complex in Q15 Format)
Cortex-M0 :
175 375
Cortex-M0+ : 136 296 cycles
Cortex-M3 : 41 430 cycles
Cortex-M4 : 18 480 cycles
Now it is up to you to select the right Frequency and suitable STM32 MCUs, it is always a compromise. Be aware that our STM32F1,F0 and L1 ADCs are able all to process a sample each 1µs and some others even at 0.2µs on our F3 ( Cortex-M4) devices which I recommend to have a look if you need faster ADCs up to 5MSPs.
Cheers,
{STOne-32}
