[Kst] How to set up an event watching zero crossings and detect phase shift?

Svenn Are Bjerkem svenn.bjerkem at googlemail.com
Tue Jan 6 14:58:16 CET 2009

I am using kst to watch the baseband output of a RF system. The bit
encoding is binary phase shift keying.
When looking at a pre-recorded communication sequence I observe that I
can look at the time difference between the zero-crossings of the sine
wave to detect the phase shifts. When a phase shift occurs, there is a
longer time to the next zero crossing, hence the bit value is changed.

What I think I need to do is:
* keep track of positive and negative going zero-crossings of the sine
wave (fixed frequency)
* Compare the time difference of the current crossing with that of the
last crossing, if larger than usual, then it is a phase shift.
* when a phase shift occurs, place a marker to indicate bit shift.

For each bit-time there is about 12 crossings. I would also like to
place a marker of different colour every 12th crossing unless a phase
shift occurs to indicate bits.

Is this possible with the event monitor, presumed that my description
could be understood?
Can an event monitor be run on pre-recorded data, or must the data be
live-streamed into kst for it to work?

Kind regards,

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