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Re: [Discuss-gnuradio] USRP2 PPS and REF

From: Eric Blossom
Subject: Re: [Discuss-gnuradio] USRP2 PPS and REF
Date: Tue, 10 Feb 2009 12:04:36 -0800
User-agent: Mutt/1.5.18 (2008-05-17)

On Tue, Feb 10, 2009 at 10:48:18AM -0600, Douglas Geiger wrote:
> Eric Blossom wrote:
> > 
> > You have to tell it to use them.
> > 
> > Take a look in <usrp2/usrp2.h>:
> > 
> >   config_mimo(MC_WE_LOCK_TO_SMA)
> >   sync_to_pps()
> > 
> > There are python bindings for these.
> > (Oops, looks like we're missing the python binding for config_mimo...)
> > Are you using this from Python?  If so, I'll fix this later on today.
> > 
> > Eric
>  On a related note. If I have two (or more) USRP2's locked onto my 10MHz
> and 1PPS signal (calls to ->config_mimo(MC_WE_LOCK_TO_SMA) and
> ->sync_to_pps() return true, so I believe they are), do I need to do
> anything else special?
>  I'm working C++, based on the rx_streaming_samples.cc code - I have two
>  usrp2 sptr's, u2a, and u2b (each created with a separate make() using
> the specified mac address from the command line).
>  Once I start streaming samples (making two calls:
> u2a->start_rx_streaming(0), and u2b->start_rx_streaming(0)), and then
> with two different handlers for receiving the samples:
>  bool oka = u2a->rx_samples(0, handlera.get())
>  bool okb = u2b->rx_samples(0, handlerb.get())
> Where the handler is just writing to the specified files.

>  I'm getting some odd results: both files typically end up with exactly
> the sample results (i.e. in octave, subtracting the results of one from
> the other results in all zeros).
> Since I've now tried this a few times
> doing things like: removing the antenna from one (and not the other),
> moving them far apart, etc. - I'm fairly certain this is a software
> problem, and not the correct results.

OK.  Just to be sure, are you explicitly specifying different mac
addresses in the calls to usrp2::make?

>  I can post my code if that would be helpful - I'm hoping I'm just
> making some silly mistake with my calls to rx_samples, and the copy
> handler or something similar. 

Please post a link to your code.

> E.g., should I be using different channel numbers?

Nope, channel number zero is the only one you need.

> I just updated the firmware on my USRP2's to r10377, and the fpga
> bitstream to r10183.


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