You'll need to make certain that the MTU on your network card supports
the required frame sizes for your FFT.
On 1GiGe, you're unlikely to be able to support greater than 1024-bin
FFTs, since most cards won't do jumbo frames larger than 9000 bytes.
On 2017-07-17 11:38, Sanjoy Basak via USRP-users wrote:
> Hello experts,
> I am trying to use RFNoc fft examples (rfnoc_fft.grc). I started with the
> gr-ettus examples. However, I am having some problems with the fft size. In
> the grc block, I find the option to choose 4096 fft size. However, with
> hardware I could only work fft size 128 and 256. If I use 512/1024 fft size,
> I get the timeout (following message) with signal source.
>
> timeout on chan 0
> timeout on chan 0
> timeout on chan 0
> timeout on chan 0
>
> Similarly, if I am receiving with RFNoc radio, with fft size 256 I see the
> correct output. However, with 512 fft size I get the following output.
>
> Ooverrun on chan 0O
> overrun on chan 0
> Ooverrun on chan 0O
> overrun on chan 0
> Ooverrun on chan 0O
> overrun on chan 0
> Ooverrun on chan 0
> O
>
> I also used the following commands to increase rf buffer size, however, the
> results are the same.
> sudo sysctl -w net.core.rmem_max=33554432
> sudo sysctl -w net.core.wmem_max=33554432
>
> I attached the uhd_usrp_probe output.
>
> I am using ubuntu 16.04. I conected the X310 with 1Gb ethernet cable.
> My hardward setup is X310/UBX-160. I am also attaching the grc file. Please
> let me know what is going wrong.
>
> Best regards
>
> Sanjoy Basak
>
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