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 > > Michael Skaggs > M.S. - Computer Engineering > LinkedIn <https://www.linkedin.com/in/MichaelDSkaggs> | Resume > <http://goo.gl/NBEs2y> | Research Cluster <http://eclipse.umbc.edu/> > University of Maryland, Baltimore County > > On Thu, Apr 21, 2016 at 11:57 AM, Marcus D. Leech <[email protected] > <mailto:[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] <mailto:[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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