[USRP-users] time_spec_t GPS Time or UTC?

Peter Witkowski pwitkowski at gmail.com
Wed Dec 10 15:10:56 EST 2014


Hello,

I have a question regarding the time reference used by the USRP (namely the
x300).

If I call the following UHD API functions (see list below), what time
reference is used (GPS or UTC)?  Does the USRP itself handle leap seconds
and the delta between Unix time and the time it's getting from it's GPS
receiver (assuming a GPSDO is installed and locked)?

1.  When I specify the time_spec_t value in issue_stream_cmd(), what time
reference is the USRP expecting?  For example, do I pass it seconds after
epoch (Unix time) or something else?
2. When I get time via get_time_last_pps(), what is the time reference?
3. Same question as above except for retrieving time via
get_mboard_sensor("gps_time").
4.  When I get samples from the sensor using recv(), what time reference is
used for the time_spec_t timestamp in the rx_metadata_t structure?  I
understand that is the timestamp of the first sample, but is the timestamp
seconds after epoch (i.e. Unix time) or based on something else?

Just wondering if I need to worry about translating between GPS seconds and
Unix seconds or something similar.

Thanks in advance for the help.

-- 
Peter Witkowski
pwitkowski at gmail.com
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