Two RX paths


#1

Hi,

Is there an example where two usrp sources are used to sample from two
daughtercards simultaneously? Or is this even possible?

Best Regards,
juha


#2

RTFM.

gnuradio-examples/python/multi-antenna/multi_file.py

Even four channels seems to be possible, using BasicRX, and special
firmware. Has anyone successfully done multi_usrp with four channels
per USRP?

juha


#3

On 12/03/2013 12:00 PM, Nemanja S. wrote:

        ),
    )

You should probably start with a GRC flow-graph with a single UHD USRP
source, with two channels being what you want, and look at the generated
Python code.


Marcus L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org


#4

Thank you Marcus again,

I changed device address, in both places, but the same problem appears.
I
see that it loads now 4rx image, but the problem remains.

    self.uhd_usrp_source_1 = uhd.usrp_source(
        device_addr="fpga=usrp1_fpga_4rx.rbf",
        stream_args=uhd.stream_args(
            cpu_format="fc32",
            channels=range(1),
        ),
    )

#5

I did following: I made simple flow graph and used USRP source first
with
two channels and LFTX mboard. But the follwong error occurs:

File “/home/savi_ne/work/gnuradio/GRC/top_block.py”, line 105, in
init
self.uhd_usrp_source_0_0_1.set_center_freq(433900000, 1)
File
“/usr/local/lib64/python2.6/site-packages/gnuradio/uhd/uhd_swig.py”,
line 1872, in set_center_freq
return _uhd_swig.uhd_usrp_source_sptr_set_center_freq(self, *args)
RuntimeError: vector::_M_range_check

When I tried with setting two mboards, with LFTX A channel subdevice in
the
first channel (B:A option_ and WBX on the second channel I get following
error:

File “./top_block.py”, line 101, in init
self.uhd_usrp_source_0_0_1.set_subdev_spec(“A:0”, 1)
File
“/usr/local/lib64/python2.6/site-packages/gnuradio/uhd/uhd_swig.py”,
line 1831, in set_subdev_spec
return _uhd_swig.uhd_usrp_source_sptr_set_subdev_spec(self, *args,
**kwargs)
RuntimeError: vector::_M_range_check

And as far as I have seen GRC doesn’t put anything in the field
device_addr
for changing FPGA image.


#6

So everything worked fine except I got the following warning:

UHD Warning:
Mixing real and quadrature rx subdevices is not supported.
The Q input to the real source(s) will be non-zero.

Which is probably due to my wish to use WBX with IQ and only one channel
from LFTX. Is there any way to overcome this problem, and is there any
explanation why this happens, cause when I use only LFTX, and
particularly
one channel (let say I), the Q is automatically produced within FPGA and
I
finally get complex baseband. Havung this in mind, why would UHD
complain
about real and wuadrature subdevices.

Cheers,
Nemanja


#7

Everything is OK, I have just put “B:A A:0” in the subdevice field.