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arm_cmplx_mag_f32() producing all-zero output

AlaaM over 6 years ago

Hi,

I'm trying to use arm FFT from the DSP library. The provided example (arm_fft_bin_example) is working, but once I use my own sinus wave values, I see an unexpected behavior.
The values in arm_fft_bin_example_f32.c look quite small, and looks like they're normalized around 0 mean and 1 std (-0.05 mean and 1.35 std).
My data consists of a sinus wave of 12 bits ADC samples, so the numbers are quite large. The result is that after the call to arm_cfft_f32() the processed numbers become even larger, and then arm_cmplx_mag_f32() returns all-zero array for the output FFT data.
My question is whether I should pre-process my data (e.g. normalize it) before using the FFT functions, or if there might be anything else that I'm doing wrong that's leading to having all-zero FFT output array.

Thanks in advance