These days I am trying to synchronize two USRP2 with PPS signal and UHD. The two USRP2 is connect with same reference clock and PPS signal. I use function "set_time_next_pps(uhd::time_spec_t(0))" to set time to be zero, and make two USRP2 start sampling after 3 seconds. The result shows that there is still phase difference, which means a delay( about 30ns) between USRP2s. I used 10MHz reference clock as input and set DDC frequence to 10MHz. Then I get two complex DC signal. The phase difference is about 0.3*2pi. It seems that the PPS impedence difference between USRP2s is the reason of delay. Any clues or solution???
You need to configure the usrp2 to use the external reference. Did you run set_clock_config(...) prior to setting the time?
(making an example of this is on my whiteboard TODO list)
By the way, the stream mode " STREAM_MODE_NUM_SAMPS_AND_DONE" does not work with "set_time_next_pps" function. It works with "set_time_now". But stream mode " STREAM_MODE_START_CONTINUOUS " works well with "set_time_next_pps" function.
When performing set_time_next_pps(...) you will want a sleep(1) prior to starting streaming. Because it could take as much as 1 second for the registers to latch the new time value.
-Josh _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
