v1.7 - Jun 2019
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Audio Thresholds
The sound on the BlueFlyVario hardware switches on and off based on the measured vertical speed.
The settings liftThreshold, liftOffThreshold, sinkThreshold and sinkOffThreshold control when the
sound comes on and off. The graph below describes how this works and what the defaults are. It is
ok to set the on and off thresholds to the same value, but you will get funny results if the off
threshold is higher than the on threshold.
Essentially what happens as you enter lift is that the vario senses a decreasing pressure. Note that
there is a slight delay between the movement and the sensed lift due to the way the filtering works.
An updated value of filtered lift gets calculated from each pressure measurement, 50 times a second
(or every 20 ms). The first time the lift goes above the liftThreshold a beep commences for a
duration controlled by the beep cadence formula (see below). That beep will last for as long as the
beep cadence, then a period of silence is commenced, this time based on the most recently
measured lift duration. Only at that time 'beeping' could end, but if the lift continues to be above
liftOffThreshold, then another sequence of beep followed by silence will be played.
