Board Mounted GPSDO (OCXO) Recommended for USRP X300/X310

• Receiver type: 50 channel with WAAS, EGNOS, MSAS
• 10 MHz ADEV: 5e-11 over >24h
• 1PPS RMS jitter: <50ns 1-sigma
• Holdover: <20us over 3h

usrp->set_clock_source("gpsdo");
usrp->set_time_source("gpsdo");

That will lock the reference clock to the disciplined 10MHz oscillator, and will make the USRP listen for time signal pulses coming from the GPSDO.

However, you will still need to explicitly set the device time on such a PPS edge, using the set_time_next_pps or set_time_unknown_pps calls.

GPS data is obtained through the mboard_sensors interface. To retrieve the current GPS time, use the gps_time sensor:

usrp->get_mboard_sensor("gps_time");

GPS

while(! (usrp->get_mboard_sensor("gps_locked",0).to_bool()) ) {
    std::this_thread::sleep(std::chrono::seconds(2));
}
usrp->set_time_source("gpsdo");

GPS sensors

Other information can be fetched as well. You can query the lock status with the gps_locked sensor, as well as obtain raw NMEA sentences using the gps_gprmc, and gps_gpgga sensors.

Location information can be parsed out of the gps_gpgga sensor by using gpsd or another NMEA parser.

TCXO和OCXO