Re: [Discuss-gnuradio] grc amplitude demodulation questions

[ematlis]

--- On Fri, 1/14/11, Josh Blum <address@hidden> wrote:

> From: Josh Blum <address@hidden>
> Subject: Re: [Discuss-gnuradio] grc amplitude demodulation questions
> To: address@hidden
> Date: Friday, January 14, 2011, 2:14 PM
> 
> > I believe the code is already doing this.  Here
> are code segments for
> > 2 fft guis.  The first shows the fft of the raw
> output of the USRP2.
> > This gui responds correctly.  Notice the line:
> > "sample_rate=100e6/usrp2_decim", so I assume that as I
> dynamically
> > adjust usrp2_decim, this value is being updated. 
> However, with the
> > second fft, while there is a similar line:
> > "sample_rate=100e6/usrp2_decim/sw_decim" that includes
> the software
> > decimation value, this fft gui does not correct the
> position of the
> > fft when I dynamically change sw_decim.  The
> x-axis DOES change, but
> > the peaks in the spectrum just stay fixed in their
> relative
> > positions.  Any thoughts?
> > 
> 
> Where else is sw_decim used? Is it used in a parameter that
> can be
> changed at runtime? Look at the generated source code, see
> set_sw_decim
> 
> -Josh
Josh-

here are the two definitions generated by GRC, one to set the USRP2 decimation 
(via a variable slider), the second to set the "audio decimation" used in the 
AM Demod block:

        def set_usrp2_decim(self, usrp2_decim):
                self.usrp2_decim = usrp2_decim
                self.wxgui_fftsink2_0.set_sample_rate(100e6/self.usrp2_decim)
                self.wxgui_scopesink2_0.set_sample_rate(100e6/self.usrp2_decim)
                self.usrp2_source_xxxx_0.set_decim(self.usrp2_decim)
                self._usrp2_decim_slider.set_value(self.usrp2_decim)
                self._usrp2_decim_text_box.set_value(self.usrp2_decim)
                
self.wxgui_scopesink2_0_0.set_sample_rate(100e6/self.usrp2_decim/self.sw_decim)
                
self.wxgui_fftsink2_1.set_sample_rate(100e6/self.usrp2_decim/self.sw_decim)
                self.high_pass_filter_0.set_taps(firdes.high_pass(1, 
100e6/self.usrp2_decim/self.sw_decim, 100, 20, firdes.WIN_HAMMING, 6.76))



        def set_sw_decim(self, sw_decim):
                self.sw_decim = sw_decim
                self._sw_decim_slider.set_value(self.sw_decim)
                self._sw_decim_text_box.set_value(self.sw_decim)
                
self.wxgui_scopesink2_0_0.set_sample_rate(100e6/self.usrp2_decim/self.sw_decim)
                
self.wxgui_fftsink2_1.set_sample_rate(100e6/self.usrp2_decim/self.sw_decim)
                self.high_pass_filter_0.set_taps(firdes.high_pass(1, 
100e6/self.usrp2_decim/self.sw_decim, 100, 20, firdes.WIN_HAMMING, 6.76))
> 
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