Re: [Discuss-gnuradio] Modifying USRP-related code (C, FX2 f/ware & FPGA f/ware)

[Eric Blossom]

On Wed, Jun 21, 2006 at 10:52:57AM +0100, Kalen Watermeyer wrote:
> Hello,
> 
> Apologies for this simple set of questions - I'm a
> relative newcomer to developing under Linux.

Welcome.

> I am trying to modify the USRP code framework to
> handle some custom hardware I've designed which also
> uses the FX2 though with a different FPGA (Spartan-3).

Shouldn't be too hard... (famous last words).

> I'm running Ubuntu Dapper and have gotten all the
> gnuradio packages, passed their configure sanity
> checks, run make && make install on all - everything
> is built.
> 
> I now need to modify the top-level usrp interface C
> code (usrp_standard.cc ?), the usrp firmware
> (usrp_common.c?), and eventually create my own FPGA
> bitfile to be downloaded. 

OK, before you start chopping away, I suggest modifying the FX2 code
so that it knows how to load your FPGA.  I don't think that'll require
many changes to the host code (the default name for the firmware and
fpga image it loads).

Start by writing a small test program that uses usrp_basic.h to load
everything, or something like usrper.cc which uses only the low level
primitives to get FX2 firmware and the FPGA bits loaded.

> I'd like to have a setup whereby I modify a particular
> source, run make to build the affected app and therby
> generate a modified binary. Are the default make
> output paths setup to handle this - should they point
> to /usr/local/bin? or to some dir in my /home
> directory?

You can specify a --prefix=<foo> argument to configure and it will
install there.  By default it goes in /usr/local.

> Also, will the top-level python scripts which call
> have to change in their function/method calls? I'd
> assume that provided the C code has been built
> successfully they'll just call the new code.

If you use the same classes and same methods, the python code will
work as is.  The python code wraps usrp_standard_rx and
usrp_standard_tx, admittedly through an excessively convoluted path.

> Many thanks for any help - and sorry again for my lack
> of knowledge on how to get things done under Linux!

Good luck.

> Cheers
> Kalen Watermeyer
> 
> I assume that the make files have been setup to invoke
> the right compilers/swig etc depending on the sources
> that have changed.

Yes.

Eric