Re: QT block to plot datapoints as they come in and keep history

[Marcus D. Leech]

On 12/18/2019 06:42 PM, Lukas Haase wrote:
> Hi Julian,
>
> Thanks for the pointer.
>
> If you have any idea how to proceed with this would be much appreciated:
>
> [  4%] Generating moc_scope_impl.cxx
> usr/include/boost/type_traits/detail/has_binary_operator.hp:50: Parse error at 
> "BOOST_JOIN"
> lib/CMakeFiles/gnuradio-rollingscope.dir/build.make:62: recipe for target 
> 'lib/moc_scope_impl.cxx' failed
> make[2]: *** [lib/moc_scope_impl.cxx] Error 1
> CMakeFiles/Makefile2:135: recipe for target 
> 'lib/CMakeFiles/gnuradio-rollingscope.dir/all' failed
> make[1]: *** [lib/CMakeFiles/gnuradio-rollingscope.dir/all] Error 2
> Makefile:140: recipe for target 'all' failed
> make: *** [all] Error 2
>
> Thanks,
> Luke
>
>   
>   
>   
>
> Gesendet: Mittwoch, 18. Dezember 2019 um 16:42 Uhr
> Von: "Julian Arnold" <address@hidden>
> An: "Lukas Haase" <address@hidden>
> Cc: "discuss-gnuradiognu.org" <address@hidden>
> Betreff: Re: QT block to plot datapoints as they come in and keep history
>
> Hey,
>   
> I had similar requirements a few years ago and came up with a rolling-scope block:
>   
> https://github.com/RWTH-iNets/gr-rollingscope/[https://github.com/RWTH-iNets/gr-rollingscope/tree/master/lib]
>   
> I haven't used this code for quite a while so no guarantees but maybe it can serve as a base for your own implementation.
>   
> Hope that helps!
> Cheers,
> Julian
>   Am 18.12.2019 um 22:30 schrieb Lukas Haase <address@hidden>:
>   
> Hello,
>
> I have a block which computes a distance and outputs this distance regularly 
> (10x per second) via a message.
>
> I am looking for a way to plot this distance over time: Basically, whenever a 
> new update comes in, it should show this value while keeping a certain amount 
> of past samples so that the distance can be seen over time.
>
> I played with the QT GUI Time Sink for quite some time (playing with sample 
> rate, update period, sending a vector of same numbers in the message or sending 
> just a vector with one element). The value updates but it only shows the point 
> at t=0 which moves up and down on the y-axis ... but I do not get the history 
> over time.
>
> I also tried implementing a "message-to-sample" converter that works like this:
>
> def incoming_msg(self, msg): # whenever new message comes in, update our state
>    if pmt.is_f32vector(msg):
>       dist = pmt.to_python(msg)
>       self.distance = dist[0]
>
> def work(self, input_items, output_items): # this is a source block
>     output_items[0][:] = self.distance # for each block, just output constant 
> signal
>     return len(output_items[0])
>
> Now I see a constant line that shifts up and down regularly, but still no 
> distance-vs-time plot.
>
> Any suggestions?
>
> Thanks,
> Luke
>
>
>   
For low-rate stuff, I've tended to just use a vector-display block, and 
then some python helper code to update that vector from time to time.
  This is great for a "stripchart" for science things like radio 
astronomy.  Not that useful for higher-rate stuff.