[USRP-users] USRP B210 RX channel alignment
Marcus D. Leech
mleech at ripnet.com
Mon Sep 29 16:13:49 EDT 2014
On 09/29/2014 04:04 PM, Chris Evans via USRP-users wrote:
> I believe I might be running into the same issue that Stefan Ereth
> wrote about on 05/02/14 and maybe also what Robert Kossler wrote about
> on 05/23/14 regarding phase alignment of USRP B210 RX channels. I have
> a 2:1 splitter feeding both RX ports on the B210 and I'm using code
> similar to examples/rx_multi_samples.cpp. When I receive data from
> both channels, there is a seemingly random phase offset between the
> two sinusoids each time I run the program. However, if I
> issue_stream_cmd() multiple times in one program, the relative phase
> between the two received sine waves is the same.
> If I use GNURadio to receive on two channels, I consistently get the
> same relative phase offset. The relative phase offset seen in a
> GNURadio scope is the same as what I see when chipscoping the outputs
> of both DDCs.
> Using chipscope, I see that with GNURadio, radio_0/run_rx and
> radio_0/strobe_rx go high at the same time that radio_1/run_rx and
> radio_1/strobe_rx go high. With my UHD program, one channel starts
> receiving before the other (and I assume the other one starts
> streaming at some later time determined by software).
> How can I force both channels to receive synchronously?
> Chris Evans
> Systems Engineer
> Azure Summit Technology, Inc.
> 3050 Chain Bridge Road, Suite 600
> Fairfax, VA 22030
> 919-428-6243 (cell)
> USRP-users mailing list
> USRP-users at lists.ettus.com
I would recommend you look at the way gr-uhd commences streaming on a
multi_usrp object--it does some timed streaming, which will likely
arrange for things to start at more-or-less the same time.
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