If the PPS GPIO is exposed to a signal with high frequency changes, a lot of
interrupts are scheduled and the handling of these calls can worst-case
starve flight critical processes leading to a loss of
control. Since PPS is not flight critical, we now give up the PPS
functionality and stop the interrupts to prevent the starvation of other processes.
The existing implementation has about 100ms difference to a reference clock. With the changes this error less than 25us.
- Use sensor_gps messages with hrt timestamps as RTC reference and not the system realtime clock. The PPS interrupt can then be aligned with the GPS clock system.
- Keep fallback based on system RTC when no PPS pulse was captured
Daniel Agar