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Forum: FPGA, VHDL & Verilog Regarding FFT v5.0 pipeline streaming


Author: varun maheshwari (Company: DEI) (varun_agr)
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Kind Atten: Lothar Miller

I am using FFT and IFFT in FFT Transform 5.0 core.I am getting correct 
result in Radix 2 burst mode, 128 transform size, natural order i/p and 
o/p width 13 bits and scaled. I am giving an array(128 samples taken 
from ADC from zero crossing) to FFT core and IFFT .But when I Taken 
samples random(128 samples and not from zero crossing) my o/p is not 
proper.why it so? Secondly, Now I implmented pipeline streaming(others 
configuration same) in place of Radix 2 then o/p is zero. In this case I 
am using array( from adc o/p 128 sample) and then fft and ifft( same as 
in radix 2) and taking next 128 samples 127 samples(old)+1 new 
sample(but in radix 2 all 128 samples are new). sir why o/p is coming 
zero and I am using loading and unloading same as radix 2. I am writing 
correct code or not . What i have to modified when I changed radix 2 to 
pipeline streaming( except scaling in radix 2 14 bit ii.e.01010101010101 
and in pipeling 8 bit 01101010).Kindly sort my problem and give me 
suggestions.

Author: Karsten M. (LMU) (Guest)
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Even after reading your posting twice I have no idea what you mean.

The pipeline streaming is the easiest mode, since it only needs a 
"start" to run an gives you all information, just as index_k, the number 
of the freq provided.

Author: Lothar Miller (lkmiller) (Moderator)
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> Kind Atten: Lothar Miller
I'm sorry, I don't have any knwoledge about the FFT cores of any 
supplier...

> I am using FFT and IFFT in FFT Transform 5.0 core.
Others who may be able to help should know: Which core on which FPGA?

Author: Karsten (Guest)
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i guess it is not xilinx, since they go with fft 7.2 ... 8.0 whilest 
the newer ones operate with axi only

Author: varun maheshwari (Company: DEI) (varun_agr)
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I am using Xilinx 10.1 and FPGA kit virtex 2 pro i.e. XC2VVP30 FF896 7C. 
I am using FFT IP core V 5.0

Author: varun maheshwari (Company: DEI) (varun_agr)
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Thanks  Karsten M. sir for showing your interest in my problem. Sir I am 
folowing query :
1. I am using ADC(giving 50 hz sine wave and 1.65 dc offset) and taking 
128 samples from zero crossing and giving these samples to FFT core and 
then IFFT core (Kindly note taking 128 samples in one cycle of sine wave 
i.e. zero to zero crossing).
 I am geting proper result but when I am taking 128 samples randomly not 
from zero crossing then getting wrong results why it so?

2.Is scaling schedule is same for radix2 burst and pipeline streaming, 
if not then what is scaling schedule for pipeline streaming.

3. In radix 2 burst mode VHDL programming , I am taking 128 samples from 
zero crossing then giving these samples to FFT core for loading samples 
and then after unloading afterwards I am using IFFT core for loading and 
unloading of data. Now again I am collecting 128 new samples from zero 
crossing(from ADC) and repeats the same steps again. (working fine)
Now in pipeline streaming I am collecting 128 samples( 127 old + one 
new) and giving to FFT core for loading and unloding and then IFFT core 
for loading and unloading. Is I am using pipeline streming right way or 
not as not getting proper output.

4. If u have some examples for pipeline streaming then send my email 
i.e. varun_agr@yahoo.com
Can anybody solve my problem?

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