Hi all,
As a follow up to my post which appears in Vol 95, Issue 1, I would be
very grateful if might be able to provide me with some answers to my
questions. A copy the email is provided below.
We currently are looking at purchasing a N3XX device but are concerned
about the practical data rates that can be achieved by the unit. We
have a E310 and the limit on this unit appears to be around the 1MSps
over the Internet connection before significant overruns occur. The
test just uses a RFNoC Radio configured as a receiver and connected to
an RFNoC FIFO prior to PS based ZMQ push sink. The E310 grc is run
with no gui using the python generated script. We use a rf signal
generator tunned to the signal of interest plus a few Hz with carrier
only. We then observe the resulting sine waves on and external the (I7
8 core host with the mtu set to 8000) and the overrun messages on the E310.
Our observations are as follows;
1. We are unable to alter the MTU size on the E310 above 1500. Could be
a kernel issue on the version we are using.
2. Changing the number of samples in a GNURadio complex vector (FIFO
length) seems to have no discernible change in the distortion on the
observed sine waves or the amount of overrun messages.
3. The distortion on the sine waves is due to system not been able to
supply samples continuously. This occurs a low sample rates as well.
4. We think the bottle neck is largely the Zynq PS processing power.
5. As the E310 uses the same Zynq PS as the N3XX we are concerned that
the Internet throughput will be as slow as the E310 unless it is
possible to bypass the Zynq processing system and send RFNoC samples
directly over the SFPs. I think this is done on the X3XX series where
the micro blaze seems to be used to set up the SFPs. I seek
clarification for how it is done on the N3XX series of devices as they
are not cheap and need to be sure of practical achievable continuous
real time sample performance.
Regards
Walter
Hi all,
Are there any RFNoC GRC examples available for the N3XX device streaming
data to a host using a SFP port??? Is the N3XX like a E3XX series in
that the GRC has to be run on the Zynq arm device or can it be
configured to run like a X3XX device where the external Host PC runs the
GNURadio, connecting the various CE blocks on the X3XX??? I assume the
Host needs to be controlling the ARM for configuration on the RJ45 port
prior to setting up communications on the SFP ports?? Does the N3XX need
to use the same approach
(https://kb.ettus.com/Streaming_processed_data_from_the_E31x_with_GNU_Radio_and_ZMQ)
as the ZMQ example to transport data to an external Host for GNURadio
processing?
I have been trying to figure out from the FPGA build and UHD driver how
it operates.? The CE engines seem to go via ADI DMAC cores where the
destination appears to be either other RFNoC CE engines on the bus or
the ARM external DDR3 memory.? Can these address the DMAs associated
with the SFPs and skip the external ARM memory DMA stage?
A top level description of how the various ingress /egress bus
communications are addressed by RFNoC would be very helpful.
Regards
Walter
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