Re: [Discuss-gnuradio] Dynamically changing bandwidth of QT GUI Frequency Sink

[Derek Kozel]

Hi Jason,

I'd recommend adding a command to the message port to update the sample rate or alternatively add support for the rate tag to the Frequency Sink and have your OOT block emit a rate tag. I'll help get that change merged if you can put up a pull request.
https://github.com/gnuradio/gnuradio/blob/219eae9a9c2ef7644450e71d19f8f54c12e1f9cc/gr-uhd/lib/usrp_source_impl.cc#L673
https://github.com/gnuradio/gnuradio/blob/a0adcd3347c7ffd6ef3c42ce7705a23978774d3b/gr-uhd/lib/usrp_source_impl.h#L29

Derek

On Tue, Jul 31, 2018 at 12:24 PM, Jason Hein <address@hidden> wrote:

Marcus,

To clarify, assume I set the sample rate at build time with the samp_rate variable within the QT GUI Frequency Sink.  At run time, the bandwidth (x axis) is reflective of this samp_rate.  However, if I have a source block upstream that changes the sample rate via out of band means, I would like that source block to change the samp_rate of the QT GUI Frequency Sink programmatically.  I am able to change the frequency of the QT GUI Frequency Sink programmatically through the message port, but I haven't seen a way to change the samp_rate/bandwidth.

Jason

On Tue, Jul 31, 2018 at 5:56 AM, Müller, Marcus (CEL) <address@hidden> wrote:

Hi Jason,
just to be sure to understand what you need:
Do you mean "zoom in x-axis"?
(because technically, the bandwidth of that display is always Nyquist,
i.e. defined by the sampling rate)

Best regards,
Marcus

On Mon, 2018-07-30 at 16:57 -0400, Jason Hein wrote:
> I have a GNU radio flow graph with a custom data source and I'd like to be able to change the bandwidth displayed on the QT GUI Frequency Sink block dynamically.  Is there a way to do this programmatically?  The QT GUI Frequency Sink block has a message port for programmatic changes to frequency, but I don't see an equivalent means for changing bandwidth.  Is there a way for an OOT block to get a reference to another block to call a public member function?

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