[Discuss-gnuradio] Disconnect parts of multiple flowgraphs

[Paul Mathews]

I have a nice gnuradio app running using USRP, with 3 FFTsinks going at
once, with the 1st FFTsink taking data from the USRP and the 2nd and 3rd
FFTsinks each showing the results of further processing:

1) USRP downconverting to 1 MHz ---> FFT display 1
2) Channel filter LP to 16 kHz ---> FFT display 2
3) AM demod and BP filter 2 to 10 kHz --> FFT display 3

I've added some code to the worker_thread class to do automatic tuning:

1) Coarse tuning based on highest peak location in FFT 1
2) Fine AFC based on highest peak location in FFT 2

Once I've located the carrier peak in FFT 1 and centered USRP tuning on it,
I have no further need to FFT and display the USRP data, and I'd like to
shut down that message queue, FFT, and FFT display to free up resources. I'm
thinking I need to 'disconnect' connected blocks, but I'm having trouble
figuring out how to do that. Any hints will be appreciated.

My attempts to naively use the 'disconnect' method consistently yield
messages like this one:

  File "/usr/local/lib/python2.5/site-packages/gnuradio/gr/top_block.py",
line 9
5, in disconnect
    self._tb.disconnect(points[0].basic_block())
  File
"/usr/local/lib/python2.5/site-packages/gnuradio/gr/gnuradio_swig_py_runt
ime.py", line 1477, in disconnect
    return _gnuradio_swig_py_runtime.gr_top_block_sptr_disconnect(*args)
ValueError: cannot disconnect block message_sink(15), not found


Paul Mathews