I am trying to receive samples from a transmitter that sends a data burst every second starting on rising edge of GPS PPS with my X310. My program structure works like this:
initialize USRP -> create stream command as MODE_NUM_SAMPS_AND_DONE and stream_now=false -> set time on USRP at next pps to 0.0 seconds -> wait 2 seconds in thread for supposed issue on PPS taking time to update -> set stream command time_spec to be time of last PPS + 1.0 seconds (so in theory, on another PPS edge) -> issue stream command -> receive samples The ref and pps sources are from external gpsdo and I can tell they are selected because the PPS LED is blinking and the REF LED is solid and external sensors are checked for lock during initialization. However, when I run this program, I am finding that the USRP is not sampling at the start of the PPS, but at seemingly random times. For example, looking at the received samples, the transmitted pulse that I know for certain is starting with the PPS is being received at 0.1, 0.2, 0.3 seconds, etc. How can I be sure that the USRP knows to sample directly on the PPS edge? -Jack Gallegos
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