Hi Lorenzo,
Regarding the SPP=364, this sounds like it is being set according to your
Ethernet transport MTU. Sometimes the NIC defaults to MTU=1500 rather than
9000. If I am right it means that even if you created a graph without K1N,
you would still get SPP=364. If the Ethernet MTU is set to 9000, I would
expect that the SPP would resolve to 2000.
Regarding the 2048 vs 2044, you might be running into a limitation there.
With the packet header bytes, the maximum payload length might not be able
to reach 2048 - I'm not really certain. But, as a test, you could try 2000
(after you resolve the SPP=364 issue).
Rob
On Mon, Feb 27, 2023 at 6:36 PM Minutolo, Lorenzo <minut...@caltech.edu>
wrote:
> Hi All,
> I am trying to build a firmware for an x300 device that uses the radio
> block and the Keep-1-in-N block using UHD 4.4.
> For my application I need the Keep-1-in-N block to operate in packet
> mode, on packets 2048 samples long.
>
> Before connecting the graph, I try to set the radio block to use packets
> of that length with the following command (C++):
> radio_control->set_property<int>("spp", 2048, 0);
> The first issue arises as, calling the function to check the spp, I read
> 2044 instead of 2048.
>
> After connecting the graph with radio RX->K1N->RX_streamer I check again
> for the radio spp and I get 364.
>
> Reading this page:
>
> https://kb.ettus.com/RFNoC_Frequently_Asked_Questions#What_is_the_SEP_buffer_size.3F
>
> I understand I could possibly use a larger packet by changing the CHDR
> width of the design. If I change the value in my YML file, I get Vivado to
> throw an error saying that 64 is the only value supported for the device.
>
> Running the design compiled with 64 bit CHDR width results in an even
> different packet size written on file.
>
> The questions are:
>
> 1. how can I make the radio to work with packets 2048 samples long in
> a x300? Does changing the SEP buffer size help? I'm currently using 8192 as
> buffer size.
> 2. why introducing the K1N block reduces the packet size to 364
> samples? how do I change this behaviour?
>
> I can share the whole code/firmware if needed.
>
> Thanks in advance for the help.
> Lorenzo
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