[Discuss-gnuradio] Conditional processing

[David R. Palchak]

I am wondering about the best method to use to perform
conditional processing.  I am implementing a packet radio
receiver that uses a sequence of pilot tones to denote the
start of a packet.  These tones are detected using an FFT. 
Once the tones are detected, I want stop performing the FFT
and start performing other message recovery processing. 
Once the incoming packet has been fully decoded I want to
disable the recovery processing and resume the FFT.

One thought I had was to implement a block that is analogous
to a signal flow valve.  This block would not write any
data to it's output until it was turned on by an external
signal.  Once on, it would be a simple pass-through stage. 


The biggest question I have is, if the valve never sent any
samples to its output, would that mean that the downstream
blocks would never get executed?  This is important because
of concerns regarding the processing capabilities of my
machine.  I won't have the power to run both the FFT and
the rest of system simultaneously.  Thus, I need to be able
to fully disengage one part while the other is running. 

Thanks,
David Palchak