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FFT/IFFT transform

Question asked by desyaterik.maxim on Jan 27, 2013

I'm trying to make forward/inverse FFT. The target is to compare, that data before, and after FFT/IFFT are equal.

// Vars definition
q15_t ADC_input[512];
q15_t RFFT_output[1024];
arm_rfft_instance_q15 S;
arm_cfft_radix4_instance_q15 S_CFFT;

// fill ADC_input  array by calculated samples

// make FFT
arm_rfft_init_q15(&S, &S_CFFT, 512, 0, 1);
arm_rfft_q15(&S, ADC_input, RFFT_output);

// now we have complex FFT values in RFFT_output, and it's Ok
// try to make IFFT
S.ifftFlagR = 1u;
arm_rfft_q15(&S, RFFT_output, ADC_input);

The problem is output array ADC_input doesn't look likes input array ADC_input.
What is wrong?