[Discuss-gnuradio] Flow with multiple sources, modulators and single sink

[Matteo Campanella]

Hello, I am trying to design a flow which implements a transmitter with two sources (a signal generator or an audio source), two modulator flows (nbfm and am) and a single sink (my hackrf device via osmosdr block).

The idea would be to make the sources and modulators switchable via a GUI drop down; since I noticed the select has been deprecated as module, my idea was to use a matrix multiplier between sources and modulators flows (2 inputs, 2 outputs) and a matrix multiplier (2 inputs one output) between modulator flows and sink.

I've noticed that this does not work. As long as I have one matrix multiplier only, with the two flows never recombining again, everything is fine; as soon as I add the output matrix multiplier, the whole graph gets stuck.

I'm pretty sure it has to do with the synchronization of blocks, but I can't find a solution... anyone has a hint of how to make things work?

The problem happens even if I swap the output matrix multiplier with an adder.

here is the grc - https://bitbucket.org/matteone/gnuradio/src/master/TX/HackRF-nbfm-am-Transmit.grc

best 73 de iz2eeq