# Top\_block start not returning

**URL:** <https://www.ruby-forum.com/t/top-block-start-not-returning/243980>\
**Category:** GNU Radio\
**Created:** [February 1, 2016, 7:01am UTC](https://www.ruby-forum.com/t/top-block-start-not-returning/243980 "2016-02-01T07:01:55Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Sadaf\_N](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/858c86/32.png) [@Sadaf\_N](https://www.ruby-forum.com/u/Sadaf_N)\
**Post date:** [February 1, 2016, 7:01am UTC](https://www.ruby-forum.com/t/top-block-start-not-returning/243980/1 "2016-02-01T07:01:55Z")

</div>

Hi,

I have a simple connection with a null source and sink, but when I try  
to start the top\_block, the start function doesn’t return. I’m simply  
using the GrTemplate project for Android. I don’t see the “Exiting  
FgStart function message,” any idea why?

gr::top\_block\_sptr tb = gr::make\_top\_block(“fg”);  
gr::blocks::null\_source::sptr src =  
gr::blocks::null\_source::make(sizeof(gr\_complex));  
gr::blocks::throttle::sptr thr =  
gr::blocks::throttle::make(sizeof(gr\_complex), 10000);  
gr::blocks::null\_sink::sptr snk =  
gr::blocks::null\_sink::make(sizeof(gr\_complex));

tb-\>connect(src, 0, thr, 0);  
tb-\>connect(thr, 0, snk, 0);

GR\_INFO(“fg”, “FgStart Called”);  
tb-\>start();  
GR\_INFO(“fg”, “Exiting FgStart function”);