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Visitor xilinx863
Visitor
316 Views
Registered: ‎03-05-2019

FFT IP

Hi, I am trying to do IFFT first and then FFT for 256 samples. so for that i wana use FFT ip to do forward FFT and Inverse FFT. I set s_axis_config_tdata(15:0) value X"0157" for forward FFT and X"0156" for Inverse FFT. Is these values is corrected?

And i am feeding 256 words of 32 bit data at input of that IFFT IP. data is like that abcdef00, abcdef04, abcdef08.......upto   ....abcdef3fc.

And getting data from FFT ip is like that afcdef00, afcdef0b, afcdef10....want to say geeting after 'a' is 'f' instead of 'b' and some bit fliping is also looking at the ending bytes.

so please somebody sugest me any solution.

I am sending some snapshots also of FFT IP configuration settings.

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2 Replies
Xilinx Employee
Xilinx Employee
281 Views
Registered: ‎09-18-2018

Re: FFT IP

Hi @xilinx863 

The TDATA of config channel contains different fields with varying bit width. Please refer to page 16 of the PG109 for the TDATA structure of the Config channel bus. From the figure present there, the FWD/INV (a one bit field)  field is in the MSB bit fields of the TDATA, while the value being changed in your example is related to LSB.

Can you please check if the the bit which is changed actually corresponds to the FWD/INV transform setting by comparing it with the bit structure.

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Moderator
Moderator
261 Views
Registered: ‎08-01-2007

Re: FFT IP

Set the IFFT and FFT output to full precision, not using scaling, you can get better results.

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