UHD, USRP1, and Twin WBX's

Hi Guys,

I have a USRP1, with a two WBX boards installed. I’m trying to use the
UHD source to get a stream from both WBX boards at the same time in
grc.

Do I need two UHD sources in my flow graph ? Or is there a way to get
a single UHD Source to give me two outputs in the way I want ? Any one
know what the magic sauce is ?

[Frequencies involved are far enough part (actually entirely different
bands) to need both boards]

When I configure the flow-graph with two UHD sources, it starts to get
data from both, but then stops after a few seconds with the following:

UHD Error:
The receive packet handler caught an exception.
AssertionError: libusb_submit_transfer(_lut) == 0
in virtual void libusb_zero_copy_mrb::release()
at /home/iain/src/uhd/host/lib/transport/libusb1_zero_copy.cpp:90
UHD source block got error code 0xf

Not sure if this is just an issue with not enough puff on my particular
USB bus, or if it’s one side of the URSP stomping on the other…

Attempting to create with just one UHD source (and two Mboards with
different sub devices [A:0 and B:0], with two channels causes the
following:

Traceback (most recent call last):
File “/home/iain/GRC/top_block.py”, line 101, in
tb = top_block()
File “/home/iain/GRC/top_block.py”, line 68, in init
self.uhd_usrp_source_0.set_subdev_spec(“B:0”, 1)
File
“/opt/gnuradio/lib/python2.6/dist-packages/gnuradio/uhd/uhd_swig.py”,
line 1764, in set_subdev_spec
return _uhd_swig.uhd_usrp_source_sptr_set_subdev_spec(self, *args,
**kwargs)
RuntimeError: vector::_M_range_check

Best Regards

Iain

On 01/24/2012 07:41 AM, Iain Young, G7III wrote:

Hi Guys,

I have a USRP1, with a two WBX boards installed. I’m trying to use the
UHD source to get a stream from both WBX boards at the same time in
grc.

Do I need two UHD sources in my flow graph ? Or is there a way to get
a single UHD Source to give me two outputs in the way I want ? Any one
know what the magic sauce is ?

You should use 1 source block. Set it up for two channels. Set the
subdevice/frontend specification to “A:0 B:0” to put dboard slot A on
channel 0 and dboard slot B on channel 1.

-Josh

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