On 2021-09-30 11:21 a.m., Adam Bader (Proxy) wrote:
We are having issues trying to run our application with the current
version 4 releases of UHD. We are running successfully on version
3.13. I've been trying to create a simplified test scenario using a
single output on a N310 and continue to see underruns and time errors
on version 4.1.
I'm using a modified benchmark_rate application trying to model our
streaming implementation.My testing has been on a system running
Ubuntu 18.04. The computer has a 10Gb card connected directly to port
sfp1 on the radio. The radio is running the default HG fpga image. MTU
is set to 9000.
Data is transmitted at 62.5Msps in a continuous burst. Every packet is
sent with an up to date time_spec. Our application builds up and sends
1ms worth of samples to the radio repeatedly (trying to pass the whole
ms to send() as well as break them up into max_num_samp chunks shows
no change in timing behavior). After resetting radio time to 0 the
initial packet is time spec'd to 1.8 seconds to prime the radio
buffer. There is no rx stream involved.
I had the sample application poll radio time in parallel with sending
data to the radio. The radio time thread prints out the result from
get_time_now every 100ms. The transmission thread prints out the
time_spec that was just transmitted once send returns. In 4.1 I can
see streaming is effectively handling everything in 'real-time'. The
radio times being printed line up identically with the time_spec that
was just transmitted. Any delay in transmission results in immediate
underruns and time errors. This same test when done with the 3.13 host
library and another N310 using the 3.13 firmware shows the sample just
written being 150-200ms ahead of what the current radio time is.
Is there anything that can be done to increase the amount of buffer
available on the radio with the stock FPGA firmware? Is there
something we need to rethink in our streaming implementation in UHD4?
Appreciate any insights.
*Are you able to do continuous (not-timed) streaming at 62.5Msps in your
current configuration?
*
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