Re: [Discuss-gnuradio] gr_add_cc use

[Josh Blum]

Only one thing may be connected to an input. You have to choose 
different input ports for the adder. Give the connect statement a tuple 
of the form (block, port_num). Like so...

fg.connect(self.packet_transmitter1, self.chan_filt1, (self.adder, 0))
fg.connect(self.packet_transmitter2, self.chan_filt2, (self.adder, 1))

Hope this helps. -Josh

Ben Olsen wrote:
> Hello,
>
> I am having a problem in trying to add multiple complex filter outputs 
> using the gr_add_cc code, I think the solution might be pretty simple 
> but I'm not very experienced with GNURadio! (I'm working on it...)
>
> Here is a code snippet: 
> ~~~~~~~~~~
> self.packet_transmitter1 = blks.gmsk2_mod_pkts(fg, spb=self._spb, 
> bt=bt, msgq_limit=2)
> self.packet_transmitter2 = blks.gmsk2_mod_pkts(fg, spb=self._spb, 
> bt=bt, msgq_limit=2)
>
> self.chan_filt1 = gr.freq_xlating_fir_filter_ccc(sw_interp,
>                                                          chan_coeffs,
>                                                          freq1,
>                                                          sw_interp * 
> self._spb)
>
> self.chan_filt2 = gr.freq_xlating_fir_filter_ccc(sw_interp,
>                                                          chan_coeffs,
>                                                          freq2,
>                                                          sw_interp * 
> self._spb)
> self.adder = gr.add_cc()
>
> self.amp = gr.multiply_const_cc (self.gain)
>
> fg.connect(self.packet_transmitter1, self.chan_filt1, self.adder)
> fg.connect(self.packet_transmitter2, self.chan_filt2, self.adder) (*)
> fg.connect(self.adder, self.amp, self.u)
> ~~~~~~~
> When I try to run this code I get a "destination endpoint already in 
> use" error at (*), so what is the correct way to add multiple streams? 
>
> Thank you so very much for your help!
>
> Ben
>  
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