Is there a chance that the issue is caused by the timed commands occurring
prior to the "set_rx_rate" command (as indicated in the code provided in
the issue tracker)? I don't know how the DDC responds to timed commands
prior to knowing its output rate.
Rob
On Mon, Jun 26, 2023 at 11:22 AM Marcus D. Leech <patchvonbr...@gmail.com>
wrote:
> On 26/06/2023 11:12, Carlo Venier wrote:
>
> Good evening to everybody,
>
> I am trying to use an X300 with two TwinRX in a coherent setup.
> After synchronization, in the case of fixed frequency operation (no
> re-tuning) the phase differences among the channels are constant and
> they remain constant over time.
> However, if I re-tune the TwinRx on the exact same frequency, I expect
> that the phase differences remain the same, but it does not happen. How
> is it possible?
>
> The LO settings are the following:
>
> multi_usrp->set_rx_lo_export_enabled(true,
> uhd::usrp::multi_usrp::ALL_LOS, 0);
> multi_usrp->set_rx_lo_source("internal", uhd::usrp::multi_usrp::ALL_LOS,
> 0);
> multi_usrp->set_rx_lo_source("companion",
> uhd::usrp::multi_usrp::ALL_LOS, 1);
> multi_usrp->set_rx_lo_source("external", uhd::usrp::multi_usrp::ALL_LOS,
> 2);
> multi_usrp->set_rx_lo_source("external", uhd::usrp::multi_usrp::ALL_LOS,
> 3);
>
> Moreover, by using the timed command before tuning all the channels
> (code snippet at "https://files.ettus.com/manual/page_sync.html";, "Align
> LOs in the front-end"), I get into the issue at
> ("https://github.com/EttusResearch/uhd/issues/606";) and the X300 is not
> usable until a power-cycle.
> I get the same issues when using both the uhd3.15.0.0 and the uhd4.4.0.0.
>
> Hopefully this bug will get fixed.
>
> I think that without timed-tuning, even though you're sharing LOs, the DDC
> phase-accumulators will be
> "ticking over" between the individual (untimed) tuning commands. So
> there will be unpredictable phase
> between all the channels.
>
>
> Should I expect the same phase differences when I re-tune to the exact
> same frequency or is it okay for the phase differences to change and I
> am missing something?
> Do you have any suggestion on how to solve the issue?
>
> Thanks,
>
> Best regards,
> Carlo Venier
>
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