Re: [Discuss-gnuradio] subdevice selection in USRP2

[Eric Blossom]

On Tue, May 12, 2009 at 03:30:09PM -0400, address@hidden 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:


>         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?

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