Start(), Stop(), run(), wait() in GNURADIO : top_block

Either you can use tb.start() + tb.wait() OR you can use tb.run() OR you can use tb.start() + tb.wait() + tb.stop()

If you have to do collect finite amount of data then you need to make a gr.head()

Generally the run method doesn't have stop.. you can see it in uhd_rx_cfile
In order to stop in such case, a gr.head() is created with finite number of samples so that the flow graph stops by itself.

All these start(), stop(), run(), wait() are boost library threads. Need to find out more by reading there.

run() = start() + wait() i.e. a call to tb.run() calls both tb.start() and tb.wait()

If you use run(), the flowgraph will not only stop, but will end its lifetime. Once run() has returned, the flowgraph is no longer usable, or as we like to say, further operations on it are "undefined." 

The run() method on a top block is really just a convenient way of telling GNU Radio your application has nothing else to do until the flowgraph exits. 


So if you want the flow graph to continue use start() and then wait()and after that stop() to stop the flow graph

Details on all of the methods can be found in gr_top_block.h as well as gr

Here is the link to important discussions :

http://gnuradio.4.n7.nabble.com/Reg-start-method-in-gr-top-block-h-tt37915.html
http://gnuradio.4.n7.nabble.com/Reg-start-wait-stop-and-run-tt37916.html

Sample example :

Try-1 :

def main():
                t = my_top_block()

                t.start()
                t.wait()
                t.stop()
                print t.c2mag.level() #print power
                time.sleep(3)
                       
                m = my_top_block()
               
                m.start()
                m.wait()
                m.stop()
                print m.c2mag.level() #print power
                time.sleep(3)
                       
                n = my_top_block()
               
                n.start()
                n.wait()
                n.stop()
                print n.c2mag.level() #print power
                time.sleep(3)

                r = my_top_block()
               
                r.start()
                r.wait()
                r.stop()
                print r.c2mag.level() #print power
                time.sleep(3)