[Discuss-gnuradio] Eye pattern code for BPSK working

[wxwize]

I've got a modification to scopesink.py, gr_trigger_mode.h, and 
gr_oscope_guts.cc to allow viewing of an eye pattern.  I added an "eye" trigger 
mode selection to the trigger menu, and an eye trigger mode that triggers on 
either a rising or falling edge (rather than only on one or the other).  When 
the eye trigger mode is selected, the last 100 traces are displayed so the eye 
pattern can be viewed.  Rather than setting the horizontal width by entering 
the number of samples per symbol, I just added some finer granularity to the 
scale selections for viewing my signal.  I also added another state to the 
trigger detect in gr_oscope_guts.cc which looks for a "pre-trigger" when the 
eye trigger mode is selected. The LOOK_FOR_PRE_TRIGGER state looks for a rising 
or falling edge followed by 3/4 symbol time without a rising or falling edge.  
Only after this condition is met does it move to the LOOK_FOR_TRIGGER state.  

The idea for this was that I wanted to trigger only on the transition within a 
manchester encoded symbol, and not on transitions between manchester encoded 
symbols (such as the transition between consecutive ones or zeros.)  I'm 
thinking I might cut this pre-trigger state out of the my final version, since 
to evaluate the openness of the eye, there is really no difference between 
intra-symbol and inter-symbol edges.  However, it might be useful as long as 
the delay (right now hard-coded to 3/4 my symbol time in samples) could be 
adjusted from the scope GUI in terms of samples.  Anyone have any 
thoughts/preferences on this?  

Finally, after I finish tweaking this, what is the best way to submit the 
changes for evaluation and possible incorporation into the next release?

Best regards,
Jon

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