Re: [Discuss-gnuradio] transmitting two independent Signals

[Robert Miller]

Hi -
I have been using the code snippet below as a reference to transmit two
signals with my USRP.  However, when trying to run the code under a peer's
newer Ubuntu installation (w/ the latest GNU Radio code), I get an error
stating that an object is unsubscriptable.  It is referring to the following
line in my code:

...
self.dst =  usrp.sink_c(nchan=2)
...
self.subdev = (self.dst.db[0][0], self.dst.db[1][0])            <---- Error
here
...

>From reading online (http://www.daniweb.com/forums/thread192533.html), I see
that this error occurs when the object that is being indexed into is
'NoneType'.   My question is why would this work on my installation and not
my peers?  Is there something silly I am not changing due to the usage of
the newer GNU Radio code (I've already made the changes from
http://www.mail-archive.com/address@hidden/msg14463.html).  Also,
receiving and transmitting from a single daughterboard work just fine on my
peer's installation.

Thanks!
Rob



Eric Blossom wrote:
> 
> On Tue, Feb 20, 2007 at 03:41:31PM +0100, anmar wrote:
>> hi all,
>> 
>> we have been searching for a way to transmit two independent signals one
>> on TxA and the other on TxB.
> 
> Using two daughterboards, you can send different complex baseband
> signals out the A side d'board and the B side d'board.  You must set
> nchan=2 in the usrp.sink_c constructor, and provide an interleaved
> stream of complexes.  (Yes, the interface is a bit strange and ought
> to be revisited/fixed.)  You can create the interleaved output stream
> using
> 
>   u = usrp.sink_c(nchan=2, interp_rate=<interp>)
> 
>   src0 = <first complex source>
>   src1 = <second complex source>
>   interleaver = gr.interleave(gr.sizeof_gr_complex)
>   fg.connect(src0, (interleaver, 0))
>   fg.connect(src1, (interleaver, 1))
>   fg.connect(interleaver, u)
> 
>   r0 = u.tune(0, u.db[0][0], freq_0)   # set center freq on side A d'board
>   r1 = u.tune(1, u.db[1][0], freq_1)   # set center freq on side B d'board
> 
> 
>> we have read the Tx_MUX documentation and tried some settings but we
>> only could send two different frequencies two only 80khz!!! and we
>> always have had two signals!
>> what we like to do is is to chose the "two independent real signal" mode
>> on the AD9862, how can we do that, just change the AD9862.h, or some
>> different approach? if yes how to load it to the USRP.
>> reading some of the forum questions, we understand that the gnuradio
>> have the "Dual channel complex" mode and changing it would give
>> conflicts with the FPGA and the software.
> 
> That's right.  If you're using a single Basic Tx daughterboard, and
> you want independent real output out the I and Q, that'll take a fair
> amount of hacking.  Using two daughterboards is going to be much, much
> easier ;)
> 
>> is there some thing that we're missing or just not understanding.
>> 
>> thanks,
>> 
>> Wim & anmar
> 
> Eric
> 
> 
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> 
> 

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