Marcus, Yes it was all coming out of the same uhd_source object. I think I was able to resolve the issue for now by setting the "Sync" parameter to "unknown PPS" which I *believe* is using the White Rabbit Ethernet based timing synchronization which we have connected at one of the SFP ports, though I need to dig in a bit more into the API.
I agree 20 ms is *HUGE*; is it unexpected even without an external timing source? Should I still be concerned? Thanks, Cameron On Fri, Nov 20, 2020 at 12:43 PM Marcus D. Leech <patchvonbr...@gmail.com> wrote: > On 11/20/2020 11:49 AM, Rob Kossler wrote: > > Hi Cameron, > Yes, this is possible. I'm not too familiar with gnuradio but in the end > you need to use a "timed start" to the receive streams. > Rob > > On Fri, Nov 20, 2020 at 7:34 AM Cameron Matson via USRP-users < > usrp-us...@lists.ettus.com> wrote: > >> Hello all, >> >> I'm trying to implement a MIMO receiver using the 4 RF chains of the >> N310. To test the timing of the system, at the transmitter I'm simply >> sending a short pulse from one transmit antenna of one USRP. At the >> receiver it looks like there is up to a ~20 ms delay/offset between the >> pairs of antennas 0/1 and 2/3 and that this delay changes each time I >> restart my GNURadio flowgraph. I can see the delay both in GNURadio GUI >> Time Sink and in actual samples that I write to file. I've tried various >> pulse widths and sampling rates at both the tx and rx, and it seems >> invariant to these. >> >> I'd really like to be able to synchronize the 4 RF chains in time >> simultaneously. Is that possible? >> >> Thanks >> Cameron Matson >> _______________________________________________ >> >> Cameron: > > Can you share a simple Gnu Radio flow-graph that displays this behavior? > A 20ms offset is *HUGE*. Are all 4 streams being streamed out > of the same uhd_source object? > > > >
