Hi Marcus, hi Pengyu, I'd like to make an addition to that: modern gr-uhd uses a timed command to start streaming samples, so the CORDICs in both USRPs should be aligned. But: It doesn't inherently use timed commands for tuning; you should do something like:
usrp_source0.set_command_time(uhd_source0.get_time_now()+0.1) usrp_source0.set_center_freq(frequency) usrp_source0.clear_command_time() time.sleep(0.15) after you configured your usrp_source and before your top_block is .start()ed. Generally, I like http://files.ettus.com/manual/page_sync.html because it explains a bit why and how things work. Greetings, Marcus On 04/24/2015 12:28 AM, Marcus D. Leech wrote: > On 04/23/2015 06:23 PM, Pengyu Zhang wrote: >> Thanks for the inspiring tips. I did not use the WX GUI scope for >> checking the phase offset. Instead, I log the baseband signal >> received by each RX antenna. Then, I plot the IQ constellation of the >> received baseband for checking their phase offset. >> >> Can you be a bit more specific when you say the "multi_usrp object" >> and the "timed commands"? Are there tutorials that I can follow step >> by step for using the two functions you mentioned? Your comments are >> very helpful :) >> > A source/sink block in Gnu Radio uses an underlying multi_usrp object, > so all you have to do is configure your source block for two channels, > with > two devices, and use > > addr0=<first-device-ip-addr,addr1=<second-device-ip-addr> > > In the device arguments. > > Also, recent gr-uhd (3.7.6.1 and newer at least) use timed commands, > so phase-zeroing will happen after a tune automatically, without you > having > to do anything. > > > The top of the UHD manual is here: > > http://files.ettus.com/manual/page_devices.htmlhttp://files.ettus.com/manual/page_devices.html > > > The Doxygen docs are here: > > http://files.ettus.com/manual/page_coding.html > > The documents for gr-uhd are part of the Gnu Radio documentation: > > http://gnuradio.org/doc/doxygen/classgr_1_1uhd_1_1usrp__source.html > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
