# Trouble reexecuting a microphone audio source **URL:** \ **Category:** GNU Radio\ **Created:** [December 9, 2014, 11:33pm UTC](https://www.ruby-forum.com/t/trouble-reexecuting-a-microphone-audio-source/233389 "2014-12-09T23:33:47Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [December 9, 2014, 11:33pm UTC](https://www.ruby-forum.com/t/trouble-reexecuting-a-microphone-audio-source/233389/1 "2014-12-09T23:33:47Z")
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: ` Linux zbox 3.2.0-4-amd64 #1 SMP Debian 3.2.63-2+deb7u2 x86_64 GNU/Linux ` and i built my gnuradio with build-gnuradio a few days ago. Here is the grc output: ` tom@zbox:~$ 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 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 ` ---
**Author:** ![Thomas\_Early](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e5b9ba/32.png) [@Thomas\_Early](https://www.ruby-forum.com/u/Thomas_Early)\ **Post date:** [December 11, 2014, 9:02pm UTC](https://www.ruby-forum.com/t/trouble-reexecuting-a-microphone-audio-source/233389/2 "2014-12-11T21:02:07Z")
Just a thought; when you stop your flow graph, are you using the big red X button in the GRC menu bar (the improper method), or closing the WXGUI sink window (the proper method)? I was doing it the wrong way for quite some time and that caused issues with hardware access. Lou Thomas Early wrote > only > clear the error by rebooting. Simply restarting grc is not enough. – View this message in context: [http://gnuradio.4.n7.nabble.com/trouble-reexecuting-a-microphone-audio-source-tp51603p51614.html](http://gnuradio.4.n7.nabble.com/trouble-reexecuting-a-microphone-audio-source-tp51603p51614.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![Thomas\_Early](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e5b9ba/32.png) [@Thomas\_Early](https://www.ruby-forum.com/u/Thomas_Early)\ **Post date:** [December 12, 2014, 2:02am UTC](https://www.ruby-forum.com/t/trouble-reexecuting-a-microphone-audio-source/233389/3 "2014-12-12T02:02:22Z")
Thanks much Lou. That was my problem. I thought I saw in a Ossmann sdr video that we were always suppose to use the big red x. I’ll have to go back and watch again. How do I stop a flow graph that only has an audio sink and no gui sink? Did I miss a link to a “intro to grc” tutorial? It took me a while to figure out an audio sink max is 1.0. ---
**Author:** ![Thomas\_Early](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/t/e5b9ba/32.png) [@Thomas\_Early](https://www.ruby-forum.com/u/Thomas_Early)\ **Post date:** [December 12, 2014, 4:02pm UTC](https://www.ruby-forum.com/t/trouble-reexecuting-a-microphone-audio-source/233389/4 "2014-12-12T16:02:13Z")
Huh, good question, I just use CTRL-C for GR programs launched from the terminal, and had no issues with hardware. If you set the GRC option block to NO GUI, I don’t recall if it even runs the flow; it may just generate the top\_block.py and you must manually launch from the terminal. In general, you don’t want a peak value of 1.0 into any hardware sink; need to back it off some. Anyway: [http://gnuradio.org/redmine/projects/gnuradio/wiki/TutorialsWritePythonApplications](http://gnuradio.org/redmine/projects/gnuradio/wiki/TutorialsWritePythonApplications) “That’s all there is to create a flow graph. The last 5 lines do nothing but start the flow graph (line 22). The try and except statements simply make sure the flow graph (which would otherwise run infinitely) are stopped when Ctrl+C is pressed (which triggers a KeyboardInterrupt Python exception).” Lou Thomas Early wrote > out an audio sink max is 1.0. > – > View this message in context: > [http://gnuradio.4.n7.nabble.com/trouble-reexecuting-a-microphone-audio-source-tp51603p51622.html](http://gnuradio.4.n7.nabble.com/trouble-reexecuting-a-microphone-audio-source-tp51603p51622.html) > Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com).