On 01/02/2011 12:59 PM, Sangho Oh wrote: > Hello Josh, > > I have used this command > > dev->send(&buff.front(), samps_to_send, > md, uhd::io_type_t::COMPLEX_FLOAT32, > uhd::device::SEND_MODE_FULL_BUFF, seconds_in_future + 0.1); > > The reference time for seconds_in_future is not clear to me. When does the > timer starts?
that last parameter is a timeout. In the example, the samples are sent several seconds in the future, so the timeout should wait at least that long. See the docs for that call: 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 > I guess there are large imprecise delay between gnuradio to USRP2 FPGA > (gnuradio -> ethernet -> FPGA). > on the order of 10s of microseconds if the CPU is keeping up. > If I synchronize two USRPs using sync_to_pps(), just wondering how to > control the transmit timing from the reference timing stamp, which is reset > every second? > The time will be set at the next pps to the desired value, and increment forever after (its a 64 bit timer). So nothing is reset or rolls over every second. http://www.ettus.com/uhd_docs/doxygen/html/classuhd_1_1usrp_1_1single__usrp.html#a7fdb91ce9c7dd16a2c4cf210ebc8105f -josh _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
