On Tue, May 4, 2021 at 12:01 PM <[email protected]> wrote:
> I was looking for a place to set those values RESIZE_OUTPUT_PACKET, 
> SIMPLE_MODE and I assumed they will be set in the yaml descriptor file 
> fft_1x64.yml under parameters section, please correct me if I am wrong.

These items are in axi_wrapper.v which is only applicable for UHD < 3.15.

> On the other hand, I was trying to find the signal “m_axis_pkt_len_t*” but I 
> did not find it, I was looking here: 
> https://github.com/EttusResearch/fpga/blob/master/usrp3/lib/rfnoc/blocks/rfnoc_block_fft/rfnoc_block_fft.v,
>  could you point me to the right place?. Also, I was looking into the RFNoC 
> specification but no luck.

For implementation of a custom FFT block in UHD 4.0 with capability
for FFT lengths > 1024, I did the following:
- used axis_data (sideband interface) in yaml
- used ctrlport_to_settings_bus (to convert to settings bus)
- used cvita_hdr_encoder & decoder (to convert to tuser 128-bit header info)
- used axi_rate_change (with M & N both set to desired FFT length)
similar to the way it's used in DDC

By using axi_rate_change (even though there is no rate change) in this
manner, this ensures that the FFT block only receives data once a full
FFT length of samples has arrived. If the upstream source sends EOB in
the middle of a block of samples, that block gets discarded.  The use
of ctrlport_to_settings_bus and cvita_hdr_encoder makes it easy to use
axi_rate_change in the manner it was designed to be used.
Rob
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