state-machine.txt

System states:

Startup: GPS active, waiting for first valid fix data; transition to daytime or dusk upon getting GPS fix
Daytime: GPS off, delay until onboard clock indicates dusk (1% drift over 24 hours = 36 minutes / day); transition to dusk
Dusk: turn on (or keep on) GPS, get fresh GPS fix; switch to night pre-

Dusk pre-event awaiting fix: GPS on, delay until we have a fix (sync once per 24 hours); transition to dusk pre-event have fix
Dusk pre-event have fix: GPS off, delay until night time; transition to night pre-event
Night pre-event: GPS off, blinking once / few seconds according to on-board clock; transition to daytime or to night event start
Night event start: GPS active, maintaining fix, blinking once / few seconds according to on-board clock; transition to night during event (fallback transition to daytime)
Dusk during event: GPS active, maintaining fix, waiting for night time; transition to night during event
Night during event: GPS active, maintaining fix, blinking once / second and doing seismic waves according to GPS PPS; transition to daytime

LOOP:
Call state-specific loop function, capture return value


Earliest civil twilight is 19:49 local / 02:49 UTC
Latest civil dawn in 06:00 local / 13:00 UTC

45 minutes dusk (say 19:04 switch-on)

Latitude, Longitude: 40 52.9' N, 119 03.8' W     Time zone: -8:00 (Pacific)     DST observance: North America
August 24
Twi: 5:46
Sunrise: 6:14
Sunset: 19:43
Twi: 20:12

UTC TIMES
Twi: 12:46
Sunrise: 13:14
Sunset: 2:43
Twi: 3:12

Latitude, Longitude: 40 52.9' N, 119 03.8' W     Time zone: -8:00 (Pacific)     DST observance: North America
September 7
Twi: 6:00
Sunrise: 6:28
Sunset: 19:21
Twi: 19:49

UTC TIMES
Twi: 13:00
Sunrise: 13:28
Sunset: 2:21
Twi: 2:49