UHD: "set_time_now" and "get_time_now" in multi_usrp

GNU Radio
1

Hi Josh and List,

There is no set_time_now in multi_usrp. When I use get_time_now which
USRP2 do I get the time of ?

BR/
Per

2

I realize that a “set_time_now” in multi_usrp would be dubious because
without any PPS all USRPs would have somewhat different times (maybe on
the order of microseconds to milliseconds). This is (typically) not
enough for MIMO applications.
However, if one is aware of this fact it can be useful. It means for
instance that one can verify that multi-usrp reception works even
without having set up PPS.

BR/
Per

3

get_time_now() returns the time on the 0th motherboard in the
configuration. The only reason you might want to read the time on a
particular board in the configuration is to test for sync.

There is some logic already in the set_time_unknown_pps() to check for
sync. Would that be useful to be brought out as a “bool
is_time_synced()” method?

http://code.ettus.com/redmine/ettus/projects/uhd/repository/revisions/master/entry/host/lib/usrp/multi_usrp.cpp#L143

_josh

4

Yes it could be useful when debugging the setup. However, it can’t be
used to verify sample-level sync.

BR/
Per