Re: [Discuss-gnuradio] input of DDC?

[Eric Blossom]

On Fri, Feb 05, 2010 at 03:22:51PM +0530, chandu wrote:
> On Thu, 2010-02-04 at 10:44 -0800, Eric Blossom wrote:
> > On Thu, Feb 04, 2010 at 03:42:10PM +0530, chandu wrote:
> > > What is the default input signal frequency of DDC of USRP(1).
> > > 1. how I and Q are given to DDC?I Q to same DDC?I Q to two different
> > > DDC's among 4 DDC's?two ADC outputs to single DDC?
> > > 2. how to give IF or only real signal to DDC through ADC? what IF
> > > frequency can we select?
> > > 3. If two receivers 900/2400 are used simultaneously how will be the
> > > ADC-MUX-DDC configuration?   
> > 
> > Chandu,
> > 
> > Please read through the USRP FAQ and take a look at the pages below.
> > If you've still got a question after reading this stuff ask again.
> > 
> > In particular look at usrp_standard_rx::set_mux
> > 
> >   http://gnuradio.org/redmine/wiki/gnuradio/UsrpRfxDiagrams
> >   http://gnuradio.org/redmine/attachments/129/USRP_Documentation.pdf
> >   http://gnuradio.org/doc/doxygen/classusrp__basic__rx.html
> >   http://gnuradio.org/doc/doxygen/classusrp__standard__rx.html
> > 
> > Eric
> 
> thank you Eric for the useful information that cleared many doubts. 

You're welcome.

> My specific doubt is:
> 
> as following statement Determine the appropriate Rx mux value as a
> function of the subdevice choosen and the characteristics of the
> respective daughterboard
> 
> int usrp_standard_rx::determine_rx_mux_value ( const usrp_subdev_spec
> &ss  )

Since you're using two daugherboards use the two subdev spec version
(It's on the next line of the Doxygen generated documentation.):

int usrp_standard_rx::determine_rx_mux_value (const usrp_subdev_spec &ss_a,
                                              const usrp_subdev_spec &ss_b)

> 
> in http://gnuradio.org/doc/doxygen/classusrp__standard__rx.html
> 
> what is the rx_mux_value for daughter boards flex900 and flex2400?

Call the function with the daughterboards installed...

If you're calling it from python this should work:

  u.determine_rx_mux_value((0,0), (1,0))


> >From whare that is loaded by default for any daughter board?  

The applications set it.  You can see this by looking at any of the
examples or utilities that we ship, or by search all the source:

  $ find . \( -name '*.cc' -o -name '*.py' \) -print | grep -vE 
'_swig.cc|_swig.py' | xargs grep set_mux

The command line is your friend...

(The grep -vE '_swig.cc|_swig.py' part filters out hits in the SWIG
generated glue between python and the C++ libraries.)

Eric