Re: [Discuss-gnuradio] Problem with symmetric behavior

[Robert Miller]

Martin,

Thanks a ton for your help.  Tuning the reciever via:

r = self.u.tune(0, self.subdev, target_freq)

did the trick.

Much appreciated!
Rob



Martin Dvh wrote:
> 
> Robert Miller wrote:
>> Hello,
>> 
>> I created a flowgraph based upon the usrp_nbfm_ptt.py example.  I am
>> witnessing some weird, asymmetric behavior when running the graph.  The
>> code
>> generates a tone from the user specified daughterboard and then plots the
>> spectrum via an fft from another user specified daughterboard.  I am
>> using 2
>> RFX-1800 daughterboards with a single USRP to run the graph, however I
>> imagine it should work the same for any RFX board.  Here is the main
>> issue:
>> 
>> Everything works fine when using Side B as the transmitter and Side A as
>> the
>> Receiver.  When running with Side A as the transmitter and Side B as the
>> receiver, however, the fft display is really just noise (once in a while
>> there exist some spectral lines at odd frequencies).  As a note, I am
>> fairly
>> certain that the mux's are being set correctly and that the boards are
>> tuning correctly.  To verify that the issue is not the hardware, I am
>> capable of running usrp_siggen.py and usrp_fft.py in both configurations
>> successfully.  (TXR A --> RXR B, TXR B --> RXR A).  Also, I have done the
>> tests in completely wired (with 60 dB of attenuation) and unwired
>> environments, with both yielding the same results.  Attached is the code
>> that I am running, can anyone point out something silly that I am doing
>> that
>> is causing this problem?
>> 
>> http://www.nabble.com/file/p14642329/DualChannel.py DualChannel.py 
>> 
>> As an added note, I am getting a segmentation fault when I close the
>> graph
>> by any means other than <Ctrl-C> from the command line.  I don't think
>> this
>> is related to the above issue, and I don't get the seg fault when running
>> the original usrp_nbfm_ptt.py code.
>> 
>> Thanks!
>> Rob
>> 
> 
> Your problem is in the tuning I think:
> 
> class receive_path(gr.hier_block):
> ....
>     def set_freq(self, target_freq):
> 
>         r = self.u.tune(self.subdev._which, self.subdev, target_freq) #
> <-- look here
> 
> Which should be:
> class receive_path(gr.hier_block):
> ....
>     def set_freq(self, target_freq):
> 
>         r = self.u.tune(0, self.subdev, target_freq) # <-- look here
> 
> The first parameter is the channel you are tuning, which is always channel
> 0 if you only receive one stream.
> It is NOT subdev._which, which indicates on which side the daughterboard
> is.
> 
> I hope this helps,
> 
> Martin
> 
> 
> 
> 
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> 

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