[Discuss-gnuradio] proper use of start(), stop(), and wait() to interact with program flow

[Ed Coleman]

I'm experimenting with writing GNUradio scripts in python. My eventual goal is to have a routine that periodically writes a floating point result from within a GNUradio process to the serial port. As a first step I wanted to try and interact with a simple routine by simply pausing after a short time period.  I started with the the following code that plays a 1kHz tone thru the sound card:

#!/usr/bin/env python

##################################################

# Gnuradio Python Flow Graph

# Title: simpleTone

# Generated: Wed Jun 29 07:26:02 2016

##################################################

from gnuradio import analog

from gnuradio import audio

from gnuradio import blocks

from gnuradio import gr

import time

class simpleTone(gr.top_block):

    def __init__(self):

gr.top_block.__init__(self)

        ##################################################

        # Variables

        ##################################################

        self.samp_rate = samp_rate = 32000

        ##################################################

        # Blocks

        ##################################################

        #self.blocks_throttle_0 = blocks.throttle(gr.sizeof_float*1, samp_rate)

        self.audio_sink_0 = audio.sink(samp_rate, "", True)

        self.analog_sig_source_x_0 = analog.sig_source_f(samp_rate, analog.GR_COS_WAVE, 1000, 1, 0)

        ##################################################

        # Connections

        ##################################################

        #self.connect((self.analog_sig_source_x_0, 0), (self.blocks_throttle_0, 0))

        #self.connect((self.blocks_throttle_0, 0), (self.audio_sink_0, 0))

self.connect((self.analog_sig_source_x_0, 0), (self.audio_sink_0, 0))

if __name__ == '__main__':

    simpleTone().run()

The code above works fine, however if I make the following substitution:

if __name__ == '__main__':

    simpleTone().start()

    simpleTone().wait()

    #time.sleep(3)

    simpleTone().stop()

The result is that the file runs, and ends after 3 seconds but no audio is produced.

I'm sure I've missed something fairly basic, any help would be appreciated. Thanks.

-Ed