Re: [Discuss-gnuradio] Receiving on both sub devices at the same time (LFRX)

[Josh Blum]

Opps, forgot to cc the list

Einar Thorsrud wrote:
> Hi all helpful GR people  :)
>
> I am trying to combine the two sub device on a LFRX card, but I can not 
> find any documentation on the USRP dual source. GRC has it's own block 
> "grc_usrp.dual_source_c", but using this (configured with GRC) I get the 
> error:
>
> TypeError: __init__() got an unexpected keyword argument 'side_b'

Can you post the python code that GRC generated for the flow graph?
side_b is a keyword argument in __init__, I am afraid that you may have
multiple versions of gnuradio installed.... What version of gnuradio are
you running?

> How can this be overcome?
>
> I am not able to find a dual source from the plain GR library, but it 
> may exist? However, I have tried to use two separate USRP sources and 
> specify separate sub devices on the two:

The USRP blocks in grc are special wrappers around the current usrp api
(to make life easier). You can use them in any custom flow graph. To
understand usage, I would take a look at the generated python code with
a usrp dual source.

also see:
http://gnuradio.org/trac/browser/gnuradio/trunk/grc/src/grc_gnuradio/usrp

> self.usrp_source_0a = usrp.source_c(0, 64) # Decimation factor: 64
> #self.usrp_source_0a.db(0, 0) # Side A, sub device A
> usrp.selected_subdev (self.usrp_source_0a, (0,0)) # Side A, sub device A
> self.usrp_source_0a.set_rx_freq(0, 0) # Set frequency 0 Hz
>
> self.usrp_source_0b = usrp.source_c(0, 64) # Decimation factor: 64
> #self.usrp_source_0b.db(0, 1) # Side A, sub device B
> usrp.selected_subdev (self.usrp_source_0b, (0,1)) # Side A, sub device B
> self.usrp_source_0a.set_rx_freq(0, 0) # Set frequency 0 Hz
>
> This however also fails. It seams the reason is that the USRP is already 
> taken by the first instance:
>
> usrp_open_interface:usb_claim_interface: failed interface 2
> usb_claim_interface: couldn't claim interface
> usrp_basic_rx: can't open rx interface

You have to do something like, create one usrp source, create 2
subdevices, and deinterleave the usrp stream into 2 streams. See the
link posted above to get an idea.

-Josh


> What then is the correct way to receive on both sub devices on the same 
> time?
>
>
> - Einar
>
>
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