On 25/05/2023 03:53, Michael Toussaint wrote:
Used a single streamer and saw the delay slightly improve to between
2.5 - 3 ns.
Any other suggestions to improve the delay to match the results from
the knowledge base, https://kb.ettus.com/USRP_N320/N321_LO_Distribution?
Also, what is synchronized mode and how can I make sure that I am
running in synchronized mode?
Thanks for your help,
Michael
Could you share how you're setting up LO sharing in your code, as well
as how you're setting the system clock on the N321?
On Wed, May 17, 2023 at 6:26 AM Rob Kossler via USRP-users
<[email protected]> wrote:
On Tue, May 16, 2023 at 8:35 PM Marcus D. Leech
<[email protected]> wrote:
>
> On 16/05/2023 20:31, Michael Toussaint wrote:
> > Hi,
> >
> > I am testing the LO synching on a single N321 using the 2 Tx
channels
> > on the N321.
> >
> > I have followed the LO setup steps from the knowledge base,
> > https://kb.ettus.com/USRP_N320/N321_LO_Distribution, to
distribute the
> > LO. (Sample Python code used for setup below)
> >
> > I am using separate streamers for each Tx channel and noticing
a delay
> > between the 2 channels executing.
> Yeah, using separate streamers, the code doesn't attempt
synchronization
> across two streamers. You'll need a single
> two-channel streamer--that's the "synchronization paradigm"
that has
> been in UHD for over a decade...
Separate streamers shouldn't be a problem. I use them regularly in
synchronized mode. If both streamers have the same time spec, the
radio should start them both in sync. That said, it won't hurt to test
with a single streamer.
> > The Tx channels do not appear to be synchronized, we're measuring
> > anywhere from 0.5ns to 4ns of delay across the channels.
The master clock cycle on the N321 is between 4 and 5 ns. This is
also the D/A (and A/D) clock cycle. When you are seeing a relative
delay of 0.5ns this is about one tenth of a D/A sample interval. Or,
from another perspective, this represents a difference of about 4
inches of cable length (if the relative delay had an analog cause).
So, the channels are definitely synchronized to some degree - I don't
have a guess at why the synchronization is not tighter.
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Chaos Industries
Michael Toussaint
Principal Software Engineer
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