Re: [Discuss-gnuradio] reading two rx channels on usrp2

[Johnathan Corgan]

On Wed, Jan 27, 2010 at 10:54, Tom Gross <address@hidden> wrote:

> Johnathan, the custom FPGA firmware you describe sounds like it might
> be perfect for what we want to do, provided it's not impossible to
> demux the data stream.

It's straightforward.  Just use gr.deinterleave(gr.sizeof_gr_complex)
after the usrp2.source_32fc block, and attach two separate complex
input block chains to outputs 0 and 1 of the deinterleaver.  Also, the
minimum decimation rate becomes 8 instead of 4 (this isn't checked
for.)

> I haven't seen any usrp2 FPGA sources (they
> don't appear to be in either the 3.2.2 or 3.3.3 tarballs) - I guess
> this means I need to figure out the new "git" stuff...

The FPGA code is not distributed as part of GNU Radio (it's a product
of Ettus Research).  It's currently hosted inside the gnuradio.org
repository, though that will be changing.  For now, though, the only
git fu you need to know is:

$ git clone git://gnuradio.org/gnuradio

...to create your own complete repository (assuming you already have
git installed.)

> it sounds like I will need to get a Xilinx compiler to build them,
> once I find them.

Yes.  FYI, the USRP2 FPGA requires the full version of the Xilinx ISE
tools; the free version won't work.  Also, you specifically need
release 10.1 with SP3.  There are currently problems synthesizing even
the standard image with newer versions of the tools.

Johnathan