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FFT - iFFT

Posted: Wed Jun 09, 2021 4:25 pm
by kheber
Hi, I see a FFT functions in the Espressif DSP Library at :
https://docs.espressif.com/projects/esp ... s.html#fft

However, it is unclear which functions are forward or backward FFT / iFFT. The documentation is very unhelpful and there are no examples given.

Can anyone provide application examples of FFT / iFFT?

Thank you

Re: FFT - iFFT

Posted: Wed Jun 09, 2021 7:55 pm
by tommeyers
Where have you looked? What did you find? (Google.com ?)

Tom

Re: FFT - iFFT

Posted: Thu Jun 10, 2021 10:48 am
by bobolink
For complex numbers you can use the FFT for the IFT:
ift = conjugate, fft, conjugate, scale
Check a math book for details.

Re: FFT - iFFT

Posted: Thu Jun 10, 2021 12:38 pm
by kheber
That's an idea; thank you. It requires unanticipated work and it should be in ASM to be fully optimized. Most other DSP suppliers have already solved that problem and written a proper iFFT for their libraries.