[Discuss-gnuradio] flow_graph.stop() hangs

[Justin Shaw]

flow_graph.stop() seems to hang on me.  This doesn't occur when I use grc, which means I most have a problem with my code.  The last line of the following code is where the problem is.

Any ideas appreciated!
Justin

def write(t, filename):
    '''
    generate and signal, transmit using usrp, then write the received data to a file
    t -- number of seconds to collect
    '''
    interp = 64
    waveform_type = gr.GR_SIN_WAVE
    waveform_ampl = 100
    waveform_freq = 20e3
    waveform_offset = 0
    target_freq = 0e3
    
    u = usrp.sink_c (0, interp)
    usb_freq = u.dac_freq() / interp
    subdev = usrp.selected_subdev(u, (0, 0))
    u.tune(subdev._which, subdev, target_freq)

    sink = gr.file_sink (gr.sizeof_gr_complex, filename)
    siggen = gr.sig_source_c (usb_freq,
                              
gr.GR_SIN_WAVE,
                              waveform_freq,
                              waveform_ampl,
                              waveform_offset)

    siggen.set_waveform(waveform_type)
    decim = 64
    frame_decim = 1
    u_source = usrp.source_c(decim_rate=decim)
    u_source.set_mux(usrp.determine_rx_mux_value(self.adc0, (0, 0)))
    input_rate = u_source.adc_freq() / u_source.decim_rate()

    # connect graph
    fg = gr.flow_graph()
    fg.connect(siggen, u)
    fg.connect(u_source, sink)
    fg.validate()
    fg.start()
    for i in range(t):
        time.sleep(1)
        print i, 'of', t
    fg.stop() # <---- this line hangs!