Hi I am confused regarding the use of the metadata for the send function virtual size_t uhd::device::send(...) http://www.ettus.com/uhd_docs/doxygen/html/classuhd_1_1device.html#a1d302f283c89b0823c9745dc395ae679
It is described as a time stamp at which the burst should be sent According to these posts : ___________________________________ http://lists.gnu.org/archive/html/discuss-gnuradio/2011-01/msg00056.html " md.time_spec is an absolute time there is a working example in uhd/host/examples/tx_timed_samples.cpp " Looking at the example (uhd/host/examples/tx_timed_samples.cpp line 84) , it says : " md.time_spec = uhd::time_spec_t(seconds_in_future); //the first call to send() will block this many seconds before sending: double timeout = seconds_in_future + 0.1; //timeout (delay before transmit + padding) " It clearly mention *seconds_in_future*, then in the comment *delay before transmit* ___________________________________ http://lists.gnu.org/archive/html/discuss-gnuradio/2011-01/msg00033.html It says that : "http://www.ettus.com/uhd_docs/doxygen/html/classuhd_1_1device.html#a11cea7a2131f2764e9afa4eab34bd8d5 The metadata specifies the timestamp of the packet: http://www.ettus.com/uhd_docs/doxygen/html/structuhd_1_1tx__metadata__t.html " ___________________________________ So what is this example setting as metadata seconds_in_future ? It looks like a delay. _ is there some flag to set timestamp as delay or absolute time ? (haven't found that in doc) _ if it is an absolute time, the timestamp represents a time at which burst tagged with timestamp should be sent. Then how is the USRP internal clock working ? Is it a counter wrapping ? starting from 0 at startup ? Is it lock to UTC if use set_time_next_pps ? I need to rely on USRP clock to send my burst on time, as my PC is not precise enough (not real-time). Is this possible to use timestamp mechanism, with a GPSDO (for stability) to send my burst accurately time wise ? Bastien _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
