FFT - iFFT

kheber
Posts: 2
Joined: Wed Jun 09, 2021 12:08 pm

FFT - iFFT

Postby kheber » Wed Jun 09, 2021 4:25 pm

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

tommeyers
Posts: 140
Joined: Tue Apr 17, 2018 1:51 pm
Location: Santiago, Dominican Republic

Re: FFT - iFFT

Postby tommeyers » Wed Jun 09, 2021 7:55 pm

Where have you looked? What did you find? (Google.com ?)

Tom
IT Professional, Maker
Santiago, Dominican Republic

bobolink
Posts: 58
Joined: Mon Feb 26, 2018 4:17 pm

Re: FFT - iFFT

Postby bobolink » Thu Jun 10, 2021 10:48 am

For complex numbers you can use the FFT for the IFT:
ift = conjugate, fft, conjugate, scale
Check a math book for details.

kheber
Posts: 2
Joined: Wed Jun 09, 2021 12:08 pm

Re: FFT - iFFT

Postby kheber » Thu Jun 10, 2021 12:38 pm

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.

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