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[Discuss-gnuradio] no packet reception when using uhd_tune_request


From: Zing Yu
Subject: [Discuss-gnuradio] no packet reception when using uhd_tune_request
Date: Wed, 31 Oct 2012 13:10:14 -0700 (PDT)

Hi All,

I have a couple of questions this time.

1) I have a setup in which I transmit gmsk packets from a tx node which are then received successfuly at an rx node (both nodes are USRP N200 radios and are being operated by GRC). However, when I turn off the cordic at two nodes by putting this line in uhd usrp sink at tx node and in uhd usrp source at rx node, I do not receive any packets at all at rx node.
uhd.tune_request(915e6, dsp_freq=0,dsp_freq_policy=uhd.tune_request.POLICY_MANUAL)
I have verified (by means of get_center_frequency() method) that the two nodes in this case are set to the same center frequency which is 914.285 MHz, so, there is no center freq mismatch between tx and rx nodes. In this case, I see some underflows at tx node and if I put a scope at rx node to see the raw received samples, then I see that the samples are not being received continuously (i.e., I see received gmsk samples for a few seconds, then noise samples for next few seconds and so on) even though the tx node is sending packets back-to-back.

2) Previously, the frequency of DUC/DDC cordic, target frequency, actual frequency used to be printed out while running any flow-graph involving usrp sink/source but it is not the case anymore. What is the easiest way to print all this info while within GRC?


Thanks,
Yu.

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