Hey Marcus, In GRC, I have a USRP Source block with "Sync" set to "Unknown PPS" and "Timing Source" set to "External". I assumed the device would be setting time based on the external PPS using these parameters. The synchronize(S0) LED goes solid (after about half a second of recording, maybe less) and the other LED (S1) is blinking with the PPS.
Thanks, Michael On Fri, Apr 22, 2016 at 11:56 AM, Marcus Müller <[email protected]> wrote: > Are you sure you're setting the device time correctly? 2.5ms offset is > definitely much much worse than what to devices that should have the same > device time should exhibit. So: > How are you setting the device time? > > Best regards, > Marcus > > > On 04/21/2016 08:59 PM, Michael Skaggs wrote: > > Aha! You were correct. I was parsing the header incorrectly. However, even > after parsing, and the more accurate values (now accurate to 10e-6), it > appears the recorded RF data sets are still are offset from each other by > an amount of nearly 2.5e-3 seconds. Any idea why this would be? It's > strange, especially considering that the are synchronized to the same PPS, > and I think the time is with reference to the pulse. > > Michael > > On Thu, Apr 21, 2016 at 11:57 AM, Marcus D. Leech <[email protected]> > wrote: > >> On 04/21/2016 11:41 AM, Michael Skaggs wrote: >> >>> I'm trying to time/sample synchronize RF recordings with two B200minis. >>> I am using the detached Metadata File Sink in GRC. Both recordings are at >>> 30MSps and both B200mini boards are synchronized to the same 1PPS signal. >>> >>> My issue is this, when I extract the data from the Metadata header file, >>> the "rx_time" value is only accurate to 10e-4 seconds (0.0001s). Which, >>> with a recording at 30MSps, this will only give me a sample alignment >>> accuracy to 10e-4(s)*30(MS/s) = 30,000 samples. >>> >>> If I'm attempting to align the two recordings by samples or time, this >>> is not nearly accurate enough. Is there a way that I can get more accuracy >>> out of my metadata header or a way that I can synchronize the recordings of >>> these B200minis? >>> >>> Thanks, >>> Michael >>> >>> The precision of the timestamps from UHD should have a precision of >> whatever the master-clock is on the device--how are you interpreting >> the rx_time tag? It's two parts--a uint64 with the full-seconds >> portion, and a double-precision float for the fractional part. >> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> [email protected] >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> > > > > _______________________________________________ > Discuss-gnuradio mailing > [email protected]https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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