Doing this before using set_master_clock_rate() on the B200 seems to
invalidate clock settings:
[HW] USRP clock set to 1759836386.000000 sec
[...]
[HW] current pps at 3.286750, starting streaming at 4.286750
In other words, the current time setting was reset. With this change
now, we see
[HW] USRP clock set to 1759929873.000000 sec
[...]
[HW] current pps at 1759929873.000000, starting streaming at 1759929874.000000
This is because changing clock sources (I assume setting the master
clock rate impacts the clock) can result in changing the time. From the
documentation of set_time_next_pps() [1]:
> Note: When changing clock sources, a previously set time will most
> likely be lost. It is recommended to set the time after changing the
> clock source. Otherwise, an unexpected time may line up with future PPS
> edges.
[1] https://files.ettus.com/manual/classuhd_1_1usrp_1_1multi__usrp.html#a75b1c5375549e6a446d686ee7d9b4e14
Robert Schmidt
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