Re: [Discuss-gnuradio] fft display frequency spotting

[Eric Blossom]

On Tue, Aug 02, 2005 at 01:54:09PM -0400, cswiger wrote:
> Gang - getting an accurate frequency reading from an fft display is pretty
> easy. This works for me:
> 
>    import wx.lib.evtmgr as em
>   ...
> 
>    # add an fft display to panel_7, nice size, avg on and weaver IF
>    # offset
>    fft = fftsink.fft_sink_c (self.fg, self.panel_7, fft_size=512, \
>      sample_rate=af_sample_rate, baseband_freq=-1.8e3, average=True, \
>      size=(680,240))
>    self.fg.connect (self.xlate_L, fft)
> 
>    # for mouse position reporting on fft display
>    em.eventManager.Register(self.Mouse, wx.EVT_LEFT_DOWN, fft.win)
> 
>   ...
> 
>    def Mouse(self,event):
>        fRel = ( event.GetX() - 48 ) / 15.2 - 20
>        print eng_notation.num_to_str(self.frequency + (fRel*1e3))
> 
> 
> Voila - just click on the peak or feature of interest and read it's
> frequency off the console. Change centers, scales and offsets to fit
> your freq range and window size.
> 
> --Chuck

Chuck, 

There's a method in gr-wxgui/src/python/plot.py that maps mouse x/y to
model space: GetClosestPoint.  The plot.py builtin example uses it.

Using it will allow you to remove the magic numbers and it also should
work when you resize the window.

Eric