Re: [Discuss-gnuradio] Using USRP w/o Daughterboard's

[Eric Blossom]

On Fri, Nov 04, 2005 at 02:19:59PM -0700, Robitaille, Michael wrote:
> Eric's reply
> 
> >From looking at the Basic RX board schematic, I can see what pins are being
> used from the high speed A/D and I have modified a connecter to input the
> signals on those pins.  It would seem that I could make the software think
> that there is a Basic RX and just feed the signal to those pins.  The Basic
> RX board is pretty simple and basically takes an unbalanced input and
> converts it to a balance input.  I followed the python code until it started
> to get into the c++ code (usrp1_source_c_sptr).  I will see about getting a
> Basic RX board but will need to modify it (John Gilmore makes mention of
> this).
> 
> I still think that there is a simple change that could be made to the code
> to make it think that there is a Basic RX.
> 

I don't think you'd need any s/w changes to use the modified Basic Rx.
The high level code will recognize the board as a Basic Rx and do the
right thing.  usrp_oscope.py and usrp_fft.py should work without mods.

> > Almost all of the high level USRP functionality is defined in two C++
> header files: 
> 
> > usrp/host/lib/usrp_basic.h and usrp/host/lib/usrp_standard.h.
> 
> > Through a somewhat convoluted path, the public interfaces of those classes
> end being methods in the Python
> 
> > usrp.source_c and/or usrp.sink_c classes.
> 
> Yes the path is convoluted, I have follow source_c in usrp.py that just
> calls usrp1.source_c in usrp1.py which call the usrp1_source_c_sptr in
> usrp1_source_c.cc. 

Basically usrp1_{source,sink}_base.{h,cc} and
usrp1_{source,sink}_{c,s}.{h,cc} are the code that glues
usrp_standard.h into the GNU Radio framework.  Generally speaking you
shouldn't have to worry about the details, unless you are planning on
adding new functionality to usrp_basic or usrp_standard.

The USRP code interfaces with GNU Radio using exactly the techniques
described in
http://www.gnu.org/software/gnuradio/doc/howto-write-a-block.html

Eric