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Observer mohamed.shfat
Observer
4,467 Views
Registered: ‎10-16-2016

XADC and FFT

Hello 

I'm trying to take an FFT on the FPGA after getting sampled data comes from XADC , but i couldn't get any results ! 

Here i figured out that the problem might be from the XADC's data , i tried to fix it but so far still no results . 

In my design i'm inserting an analog input signal to VP/VN pins on XADC header , then i'm trying to get some data comes out from the 1MSPS XADC . 

When i plot the output data it looks as it sampled correctly , but when i try to take its FFT whether on FPGA FFT CORE or on MATLAB , i get no results . The sampled signal and its FFT are shown below in the pics . 

Also i tried many frequencies for the input signal starts from 10KHz up to 480KHz , but they are all giving the same result , empty window in the Freq-domain . 

If someones know what's the problem i would really appreciate the help . 

Regards 

sampled sin with 50khz.jpg
Spectrum of the sampled sin.jpg
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6 Replies
Moderator
Moderator
4,454 Views
Registered: ‎07-31-2012

Re: XADC and FFT

Hi ,

 

Did you try to test FFT alone with out XADC?

 

Regards

Praveen


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Observer mohamed.shfat
Observer
4,438 Views
Registered: ‎10-16-2016

Re: XADC and FFT

Hi Praveen

Actually i didn't , i wanted to make the XADC debugging as a first step , i extracted the data from the XADC and i tried to take it's FFT on the MATLAB to make sure whether the problem is from the FFT IP CORE on FPGA or not , and the results that comes from the MATLAB are as same as the results from the FFT CORE output . That's why i considered that the error is from the XADC , but unfortunately i couldn't know what's it exactly or it's because of what .  

Regards sir 

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Xilinx Employee
Xilinx Employee
4,436 Views
Registered: ‎08-01-2008

Re: XADC and FFT

you may require to add chipscope and debug signals . you may bypass FFT and check XADC output. try using other IP like FIR
Thanks and Regards
Balkrishan
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Observer mohamed.shfat
Observer
4,411 Views
Registered: ‎10-16-2016

Re: XADC and FFT

First thanks too much for your reply sir , i appreciate that really . 

IN fact that's what i have done , but instead of chipscope i used ILA core because i'm working on Vivado Design Tool not ISE . 

Any way i'm already added the core and debugged the signals , and debugged the XADC individually , but the results were as same as the shown above in the post .

My problem is to know why the output signal of the XADC can be transformed to Freq-Domain even when i use the FFT function on the MATLAB , it gives me just 2 peaks at 0 and 1023 points which are the first and the last points of my FFT !

Is it beacuse of sampling rate in the ADC although the sampled signal looks fine when i display it on Time-Domain , or what's the exact problem behind that ? 

Greetings sir 

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Contributor
Contributor
849 Views
Registered: ‎02-14-2018

Re: XADC and FFT

how to give input to the xadc header is it done through dds compiler to the xadc for sampling then to the fft please do let me know

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158 Views
Registered: ‎04-22-2019

Re: XADC and FFT

Hi mohammaed,

  May i know how to obtain the Converted ADC outpur for the extrenal analog signal. Is it you used XADC wizard IP or by writing HDL program. It will be helpful to my work if you reply. My design flow is by creating block digrams and working on it.

 

 

thanking you

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