[USRP-users] RFNoC how to configure FFT block

Martin Braun martin.braun at ettus.com
Mon Oct 23 17:49:10 EDT 2017


Daniel,

FFT controls happen through the 'shift', 'direction', and 'scaling'
properties. See, e.g., here:
https://github.com/EttusResearch/uhd/blob/ec9138eb6634b0af106762832c7518c887576a94/host/include/uhd/rfnoc/blocks/fft.xml#L71-L82

The control word is constructed in the block from those settings.
However, let's say you would want to write it yourself, UHD will take
care of endianness etc. The LSB of the your write from Python will the
LSB of the register in the FPGA eventually.
Note that you don't need to do this here.

Cheers,
Martin




On 10/13/2017 01:14 AM, Daniel Rauschen via USRP-users wrote:
> Hi all,
> 
> I have some questions regarding the noc_block_fft.
> 
> Is it possible to enable/disable the parameter EN_FFT_SHIFT from Python?
> What is the effect on an inverse FFT with the implemented EN_FFT_SHIFT
> enabled?
> How to configure a inverse FFT?
> How is the "control_word" parameter properly set? I guess the
> "control_word" is passed to the Xlinx IP on the "Configuration Channel"
> see [1] page 14 to 17?
> What byte order is the write method (Python) for block parameters? Is it
> little or big-endian? If I pass a 32 bit wide parameter, do I have to
> reorder the 4 bytes?
> 
> I hope someone can help with some of my questions.
> 
> Thanks and best regards,
> 
> Daniel
> 
> 
> 
> [1] https://www.xilinx.com/support/documentation/ip_documentation/xfft/v9_0/pg109-xfft.pdf
> <https://www.xilinx.com/support/documentation/ip_documentation/xfft/v9_0/pg109-xfft.pdf>
> 
> 
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