[USRP-users] issue with rfnoc fft size

Sanjoy Basak sanjoybasak14 at gmail.com
Tue Jul 18 04:42:17 EDT 2017


Hi,
Thanks a lot for the suggestions.
I increased the MTU size to 9000. Now when I am generating signal in
computer and doing fft on FPGA (with the signal source block), I can do fft
with fft size 1024 with sample rate 200 MSps. This works perfectly without
any overrun or timeout.

However, when I am using RFnoc radio, I am getting overrun. I am having
overrun even with 1 or 5 MSps with fft size 128. I also tested with fft
size 16 (still overrun). I think there is something going wrong here. I
tried changing the gain and other setting, however, the result is still the
same. Could you please check and let me know what might occur this issue?

Best regards
Sanjoy



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Sanjoy Basak
Researcher
Royal Military Academy
Dept. Communication, Information Systems & Sensors (CISS)
30, Avenue de la Renaissance
B-1000 Brussels
BELGIUM
Tel : +32-2441 4162
email: Sanjoy.BASAK at mil.be

On Mon, Jul 17, 2017 at 6:48 PM, <mleech at ripnet.com> wrote:

>
>
> 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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