FFT/IFFT transform

[ma.x9]

Posted on January 27, 2013 at 23:13

Hi!

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?