Honored Contributor
Honored Contributorhey amrbekhit,
kaz's advice is right on about the FFT accepting 2's compliment inputs. you need to either bias your data to 0 DC or scale it so it resides in +/-2^15. i did some simulations with your FFT setup and data using Simulink and DSPBuilder (and the Altera FFT MegaCore v8.1). in this result the input data is scaled by 1/2 https://www.alteraforum.com/forum/attachment.php?attachmentid=799 in this result the input data is biased by -2^15 https://www.alteraforum.com/forum/attachment.php?attachmentid=800 you can see the DC in the first result but not the second because it was biased out. so it is possible to get useful power spectrum from your data (with a small fix) and FFT setup. what data are you sending to the FFT after your 1000 points are over? i am using zeros. i suspect your problem might be in NIOS or interfacing to the FFT core. will you be using an FFT window? it will give you much better results. i have attached a .zip of my plots in full resolution. https://www.alteraforum.com/forum/attachment.php?attachmentid=801
