On 10/26/2020 01:39 PM, Hodges, Jeff via USRP-users wrote:
I'm thinking that timed tune commands will not work on tagged streams
in burst mode. Is that correct? I've been looking at the USRP sink
block code and it supports the timed commands on the stream, but from
reading a recent thread, it seems like this will not work because of
how the DUC derives it's time:
https://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2020-March/061611.html
This thread says DUC derives it's sense of time from the samples, and
if the samples are not streaming, the DUC will not keep track of time.
Therefore, the timed command will not be executed.
For example, I set the tx_time tag to 1.0 second and the burst is 0.05
sec long. Then I place the tuning command tag on the last sample of
the burst with a tune time of 1.05. The radio does not actually tune
until I transmit the next burst at 1.1 sec (0.05 sec dead time) and
then it tunes at approximately 0.007 sec into the middle of that burst.
I can try to implement tuning during the dead time by making calls
directly to the C++ api at the appropriate time in a separate thread,
but before I do that I just want to confirm that this burst time-tag
method will not work.
Thanks in advance,
Jeff
From the quoted thread, it seems that the *radio* part of the timing
will work fine, but the DUC won't be able to do its part of the deal--so
if your tuning requires "mop up" action on the part of the DUC, it
won't work properly.
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