Re: [Discuss-gnuradio] QT GUI (Constellation Sink) Update Period (Refresh Rate)

[Tom Rondeau]

On Tue, Nov 17, 2015 at 7:40 AM, Johannes Demel <address@hidden> wrote:

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Hi David,

> 2) Should I set 'Number of Points' to 576?
Yes. The block will take this amount of points and display it. Then
wait a given time and take the next chunk to display it.
As long as the block does not have at least the specified amount of
symbols available, it will not update or display anything.

>
> 3) Update period, what is this in terms of, Hz or..., what should I
> set this to?
It should be a value in seconds. Since the sink is only updated when
enough new samples are available and you send only very few to the
sink, I recommend setting this value to 0.0. This should trigger an
update every 'Number of Points' received samples.

>
>
> Sorry if this is all detailed somewhere but I can't find it easily
> in https://gnuradio.org/doc/doxygen/page_qtgui.html

 The constellation sink also has the ability to trigger, which is based off the magnitude of the incoming complex sample.

https://gnuradio.org/doc/doxygen/classgr_1_1qtgui_1_1const__sink__c.html#a5b74b15a8807014eb85964a26d2b6d01

Set the trigger mode to TRIG_MODE_NORM and the level of the signal magnitude you want to trigger off of. If you've set the number of points to 576 and it triggers off the first sample, that should display and hold the plot until the next trigger action.

Tom