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STM32F4 FFT spectrum

Question asked by jasonas.matas on Nov 13, 2015
Latest reply on Nov 13, 2015 by Clive One
Hey, I am going to use FFT in one of my projects, and I have stumbled upon a question. The output buffer from the fft is the spectrum only in the first half of the buffer or the whole buffer is the spectrum. I found a tutorial which states that is only the first half:

http://stm32f4-discovery.com/2014/10/stm32f4-fft-example/
qoute:"We will get back an array, basically 256 length, but results from 0 – 127 are valid, results from 128 – 255 are the same results as first one, but in reverse order."

Yet in this forums discussion:
Disccusion
They use FFT length of 1024 and in the picture you can see that the spectrum goes right to the 1024.

Can someone clearify this for me?

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