We are using Quartus prime lite v17.1 to simulate and verify the FFT IP core.
FFT IP Config -
1) Variable streaming mode
2) Fixed point FFT
3) 64 points
4) 16 bit sink data
As per our requirement, - FFT IP Clock is 125MHz
We are providing valid sink_real, and sink_imag data at every 3rd clock of 125MHz. , so we keep SINK_VALID high for one clock and then low for next two clocks.
The output FFT shows one sample missing in every FFT frame, FFT IP provides only 63 samples every frame but SOP, EOP asserts /deasserts as per the 64 sample count.
so, EOP of first frame asserts at first sample of 2nd frame. and SOP of second frame asserts at the 2nd sample of 2nd frame.
I am also attaching the waveforms to understand the issue.
Please let us know why FFT IP core is showing such behavior.
Also note that, when SINK valid is constantly high for entire input, FFT output also comes correct with no missing sample.
Please clarify that is this issue related to FFT IP core itself or its about quartus version issue.
As we observed this issue persists with both Quartus 17.1 (Lite edition) and Quartus 18.1 (Lite edition, standard edition).
Please also let us know, what are the other known issues with FFT IP Core.
Thanks and Regards