Subdevice selection in USRP2


#1

Hi all-

as part of my on-going efforts to acquire 2 channels (two independent
signals) on my USRP2 with an LFRX board, I would like to know if there
is
an equivalent to the subdevice setup code that exists for the USRP1.
For
example:

     if not self.u.set_nchannels(nchan):
         sys.stderr.write('set_nchannels(%d) failed\n' % (nchan,))
         raise SystemExit

     self.subdev = self.u.db[0] + self.u.db[1]

     self.u.set_mux(gru.hexint(0xf0f0f1f0))

I already understand from a previous response on this list that there is
only a single DDC in the USRP2 fpga image, and I can at least verify
that
set_nchannels, db, or set_mux is not defined for the USRP2. Are there
equivalents with different syntax for the USPR2? Without them or their
equivalents, is it even possible to acquire two channels with the USRP2
currently?

My thought was I could get arround the existence of only 1 DDC by tuning
to the midpoint of my two signals and shifting them independently to
baseband in the host pc, but it seems to me I need more than this to
properly setup the two signal paths.

thanks,
eric


#2

On Tue, May 12, 2009 at 03:30:09PM -0400, removed_email_address@domain.invalid wrote:

Hi all-

as part of my on-going efforts to acquire 2 channels (two independent
signals) on my USRP2 with an LFRX board, I would like to know if there is
an equivalent to the subdevice setup code that exists for the USRP1. For
example:

set_nchannels, db, or set_mux is not defined for the USRP2. Are there
equivalents with different syntax for the USPR2? Without them or their
equivalents, is it even possible to acquire two channels with the USRP2
currently?

It is not currently possible to acquire more than a single channel
with the USRP2.

My thought was I could get arround the existence of only 1 DDC by tuning
to the midpoint of my two signals and shifting them independently to
baseband in the host pc, but it seems to me I need more than this to
properly setup the two signal paths.

If the two signals are within the same IF passband, then yes, you can
split them out on the host. Use the gr.freq_xlating_fir_filter_ccf.

Eric


#3

On Tue, May 12, 2009 at 04:28:44PM -0400, Eric Matlis wrote:

signals) on my USRP2 with an LFRX board, I would like to know if there is
self.u.set_mux(gru.hexint(0xf0f0f1f0))

one carrying the AM signal, the other the non-AM signal. My objective is to capture both.

So as I understand it this is not possible currently?

Yes, you understand correctly.

This should be possible after the “great refactoring” that will occur as
part of the USRP2 VRT work.

Eric