Forum: GNU Radio usrp_multi and the USRP2

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D9b2772a9387f5dbe010dbc0c3a93f8d?d=identicon&s=25 Douglas Geiger (Guest)
on 2009-02-03 21:47
(Received via mailing list)
Is there any code similar to usrp_multi.py to use multiple USRP2's
already (or is it unnecessary)? As I understand it, with the USRP2, you
either use the MIMO cable, or an external reference to synchronize the
clocks - then on the host side you would still need to do the
align_on_samplenumbers/deinterleaving, etc. business that usrp_multi.py
took care of for the USRP1.
 If nobody has code available to do this, should I expect any major
hurdles in trying to convert the usrp_multi.py for use with the USRP2
(besides converting the source create calls, removing the subdev calls,
etc)?
 If I'm using the MIMO cable, do I need to make any additional settings
(e.g. sync_to_pps(True) or similar) to synchronize the master to slave?
http://gnuradio.org/trac/wiki/USRP2GenFAQ says the VCXO locks on to the
external reference, if one exists - which implies this is also the case
for the MIMO cable, just wanted to verify that was true.
 Looking at test_mimo_tx.cc in the u2-mimo-wip branch I see it is
possible to setup one usrp2 interface, and send samples to different
channels - is that accessible from python now - or is it still code
that's in development? If that's the case, is it possible at all to get
synchronized samples out of two usrp2's with a MIMO cable right now with
python, or should I be writing something in C++ to do that for me?
 Perhaps
 Thanks,
  Doug

--
Doug Geiger
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
douglas.geiger@okstate.edu
doug.geiger@ieee.org
745d8202ef5a58c1058d0e5395a78f9c?d=identicon&s=25 Eric Blossom (Guest)
on 2009-02-03 22:24
(Received via mailing list)
On Tue, Feb 03, 2009 at 02:33:15PM -0600, Douglas Geiger wrote:
> etc)?
> python, or should I be writing something in C++ to do that for me?
>  Perhaps
>  Thanks,
>   Doug

Doug,

There's currently no production code that supports using the USRP2 and
the MIMO cable.  We have test code that confirms that the h/w works as
we expect, but we're not going to sort this out until after "the great
reworking" of the host, firmware and on-the-wire spec as part of our
move toward VITA-49 (VITA Radio Transport), an emerging standard for
digital IF.

In the meanwhile, you can make this work by providing your own
star-distributed 10 MHz reference and PPS.  All USRP2's will be
coherent and will share the same timestamps.  You will have to invoke
config_mimo(MC_WE_LOCK_TO_SMA) and sync_to_pps() on each USRP2.

Eric
D9b2772a9387f5dbe010dbc0c3a93f8d?d=identicon&s=25 Douglas Geiger (Guest)
on 2009-02-03 23:18
(Received via mailing list)
Eric Blossom wrote:
 > There's currently no production code that supports using the USRP2
and
>
> Eric

 Understood. Looking around at code that uses config_mimo (which looks
like it's only available to C++ apps right now) - I see rx_samples.cc
uses it, but it looks like that's fallen out of use, and is a bit crufty
now. Any reason I couldn't modify rx_streaming_samples.cc to call
config_mimo?
 Thanks,
 Doug

--
Doug Geiger
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
douglas.geiger@okstate.edu
doug.geiger@ieee.org
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