[Discuss-gnuradio] trouble reexecuting a microphone audio source

[Thomas Early]

I'm just getting started with grc but I am having problems already.

I have a simple flow graph: an audio source with a device name "hw:1,0" 
connected to a WX scope sink.

hw:1,0 is my Logitech headset according to 'arecord -l'.

The first time i run my flow graph after booting up, it works fine. After 
stoping 
the flow graph, any subsequent time I try to run it, I get an error. I can only 
clear the error by rebooting. Simply restarting grc is not enough.

My 'uname -u' output is:

<code>
Linux zbox 3.2.0-4-amd64 #1 SMP Debian 3.2.63-2+deb7u2 x86_64 GNU/Linux
</code>

and i built my gnuradio with build-gnuradio a few days ago.
Here is the grc output:

<code>
address@hidden:~$ gnuradio-companion
linux; GNU C++ version 4.7.2; Boost_104900; UHD_003.008.000-52-g2068af70

<<< Welcome to GNU Radio Companion 3.7.5.1 >>>

Preferences file: /home/tom/.grc
Block paths:
        /usr/local/share/gnuradio/grc/blocks
        /home/tom/.grc_gnuradio

Loading: "/home/tom/grc/playing.grc"
>>> Done

Showing: "/home/tom/grc/playing.grc"

Loading: "/home/tom/dialtone.grc"
>>> Done

Generating: "/home/tom/grc/top_block.py"

Executing: "/home/tom/grc/top_block.py"

Using Volk machine: avx_64_mmx_orc
INFO: Audio source arch: alsa

>>> Done

Generating: "/home/tom/grc/top_block.py"

Executing: "/home/tom/grc/top_block.py"

Using Volk machine: avx_64_mmx_orc
INFO: Audio source arch: alsa                                                   
                                           
ERROR: [hw:1,0]: snd_pcm_hw_params failed: Input/output error                   
                                           
Traceback (most recent call last):                                              
                                           
  File "/home/tom/grc/top_block.py", line 76, in <module>                       
                                           
    tb.Start(True)                                                              
                                           
  File "/usr/local/lib/python2.7/dist-
packages/grc_gnuradio/wxgui/top_block_gui.py", line 73, in Start                
     
    self.start()                                                                
                                           
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/gr/top_block.py", line 
104, in start                               
    top_block_start_unlocked(self._tb, max_noutput_items)                       
                                           
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/gr/runtime_swig.py", 
line 4724, in top_block_start_unlocked        
    return _runtime_swig.top_block_start_unlocked(*args, **kwargs)              
                                           
RuntimeError: check topology failed on audio_alsa_source(8) using ninputs=0, 
noutputs=1                                    
                                                                                
                                           
>>> Done 
</code>