[USRP-users] Sychnronize two USRP X310 with GPS
uqdqj at student.kit.edu
Fri Dec 19 08:10:19 EST 2014
the last weeks we tried to synchronize our two usrps X310 between two
stations with two seperate GPS antenna, but the results weren't as good
as we hoped.
For your information, every usrp is connected to his own pc on which
the same code is running.
Our first intent was to check if the gps antenna is locked
(get_mboard_sensor('gps_locked')) and then start to receive samples
with the same time given
(set_start_time(uhd.time_spec_t(self.start_time))). We only want to
receive samples, therefore we used set_start_time() instead of
When we checked the sync, there was a difference about 20 - 100 us.
According to the documentation only ~100 ns should be allowed.
We also read out the rx-time stream tags for both measurements and
compared them. However, they were identically.
In the documentation of Ettus it's explained, if the GPS is locked to
the satellites the internal VITA timestamp will be initialized to the
GPS time, and the internal oscillator will be phase-locked to the 10MHz
So if their both locked they should have the same timestamp, or? Or do
we need some further code to initialize the gps time to the usrp?
What else could be the problem?
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