Re: [Discuss-gnuradio] How to Access Received Data for Use In Changing RX Parameters

[madengr]

Jonathan Fox wrote
> Hey List,
> 
> I have two scripts I am running, the ofdm_v1_tx_freq_test.py and the RX
> version of it (see flow graph images and attached transmitter Python
> script). I am transmitting a sinusoid using OFDM modulation over the USRP,
> it works perfectly.
> 
> I have made an alteration to the transmitter script by adding a frequency
> change function that goes off every 2.5 seconds. The frequency will
> inclemently go up 1 MHz 20 times before going back to the default. That
> code works; what I want to do now is to cease the sinusoid broadcast at
> every 2.5 seconds so I can transmit the new frequency to the receiver
> right
> before I change it. I think I can figure that part out, I may just use
> another vector source with the new frequency and have transmit five times.
> Probably use another flow graph to implement it. If there is a better way
> to do, I am open for ideas.
> 
> Now for my question: after receiving this new frequency on the RX side,
> how
> do I get my script to read this data and use it to change frequencies? I
> have a feeling that this may be simple to do but I am at a loss in
> figuring
> it out.
> 
> Please note, this is more of a proof of concept work, so there is a reason
> why I do not have identical frequency change functions in both TX and RX,
> the goal down the road is to get some DSA capabilities.
> 
> Thanks,
> 
> Jon
> 
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> 
> ofdm_v1_tx_freq_test.py (7K)
> <http://gnuradio.4.n7.nabble.com/attachment/47642/0/ofdm_v1_tx_freq_test.py>
> ofdm_v1_rx.png (97K)
> <http://gnuradio.4.n7.nabble.com/attachment/47642/1/ofdm_v1_rx.png>
> ofdm_v1_tx.png (77K)
> <http://gnuradio.4.n7.nabble.com/attachment/47642/2/ofdm_v1_tx.png>

You can use a message queue to get data in and out of the flow from your
Python script.  I'm sure there are better ways, but this is what I have been
experimenting with recently.  It's just a matter of polling the queue and
clearing it when there is new data.  This is a good write up:

http://pwnhome.wordpress.com/2011/04/19/intro-to-gnuradio-and-the-usrp-part-4/




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