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How to Access Received Data for Use In Changing RX Parameters

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How to Access Received Data for Use In Changing RX Parameters

Jonathan Fox
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) Download Attachment
ofdm_v1_rx.png (97K) Download Attachment
ofdm_v1_tx.png (77K) Download Attachment
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Re: 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

_______________________________________________
Discuss-gnuradio mailing list
[hidden email]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio


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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