[USRP-users] uhd.tune_request on the fly?

Murphy, John jmurphy at comsonics.com
Fri Apr 17 15:45:54 EDT 2015

I am trying to change center frequencies in response to GUI text entry.
Other blocks in the flowgraph accept and propogate the change in the
GUI text thru a variable in GRC.
But the UHD does not appear to change frequencies "on the fly" like
this. It will only change when I stop the flowgraph, execute the
change, and re-start.

Is this the expected behavior when you pass a uhd.tune_request() to
the center frequency parameter of a UHD Source block in GRC? Or maybe
something with the version I am using anyhow? Or just something I am
doing incorrectly?

UHD 3.8.1
UHD Source Block Ch0 Center Freq
B200 (one of the old white boards)
GPSDO on board if it by some chance matters

center_freq and samp_rate are GRC flowgraph variables from QT GUI
Entries with those names
exact param is uhd.tune_request(center_freq, samp_rate / 2.0)
similarly changing samp_rate (say, between 2M and 4M) *works on the
fly* (for the samp_rate, it does not seem to change the tune request
changing center_freq from 600M-ish to 1600M-ish for instance does not
actually tune the receiver.
even though I see the rest of the flowgraph update because axis labels
on the GUI etc change
(plus I have debug printfs that pop out when I change frequencies in a
custom block)


John Murphy
jmurphy at comsonics.com

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