Hello Fabian and Young, The suggestion about timed commands is on point, I think that is what is missing. Using unknown PPS will not hurt as there are two radio blocks with timekeepers and using the unknown PPS setting, or external or gpsdo if installed, will ensure that they are aligned.
> 3) If that does not work, maybe the FPGA can handly only one command at a time - even if you tell him to execute two. Then it may be possible to start one command timed before the other and extend that sequence of samples with the correct amount of zeros. Each radio channel has it's own queue for timed commands so it is possible to schedule all channels simultaneously. Derek On Mon, Jul 30, 2018 at 8:08 AM, Fabian Schwartau via USRP-users < usrp-users@lists.ettus.com> wrote: > Hi Young, > > I am not an expert, but I have three suggestions: > 1) Using 'Unknown PSS' or any other sync method should not have no affect, > as this is for syncing two or more USRPs. You have only one FPGA and that > is in sync with itself ;) > 2) Did you tried using timed commands? (see function set_command_time()) > 3) If that does not work, maybe the FPGA can handly only one command at a > time - even if you tell him to execute two. Then it may be possible to > start one command timed before the other and extend that sequence of > samples with the correct amount of zeros. > > Best regards, > Fabian > > Am 30.07.2018 um 08:34 schrieb YoungC_Park via USRP-users: > >> Hi all, >> >> I hope someone could help me on my situation. I could not find similar >> cases on the usrp archive. >> >> I have one USRP X310 that has UBX-160(slot A) , LFTX board(slot B) and >> GPS module installed. >> >> - my UHD is 3.11.0 >> >> - Using uhd API based on tx_samples from_file.cpp, I can generate dual >> output bursts from UBX160 and LFTX with 200MHz master clock and 100Msps on >> USRP X310. >> >> - However, the second output (ch 1, red in the picture) is lagged from >> the first one (ch 0, yellow) by about (~10us with +-4us uncertainty) >> >> - The baseband burst is a sawtooth waveform of two cycles(2000 samples >> long). and UBX160 modulates it into fc = 1GHz whereas LFTX generates it as >> is. >> >> - This lagging is quite constant (10us) even if I change the sampling >> rate (10,20,50, 100MSps). >> >> - Tried 'Unknown PPS', 'gpsdo', 'internal',,, but no difference. >> >> - When I switch the order of channels to (1,0) as opposed to (0,1), then >> the ch0 lags behind the ch1, which seems that this is related to some >> sequenced process… >> >> We are seeking for helps on the cause and cure about this lagging… >> >> Thanks, >> >> Young C. Park >> >> >> >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >
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