I use ntpd with GPS NMEA with PPS as follows
server 127.127.20.0 mode 18 minpoll 4 maxpoll 4 prefer fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 flag4 0 time2 0.475
- flag1 enables PPS signal processing of /dev/gpspps0 implicitly
- flag2 captures rising or falling edge
- flag3 uses ntpd clock or kernel discipline
I have read about that flag2 could be used for polarity issues with the serial port. So if there is no problem with that I should use rising edge. Or are there any issues about a steeper edge in the falling case?
Should I use ntp clock or kernel discipline? What's the difference? I've read that min/maxpoll 4 and ntp clock discipline is better then kernels due to a median algorithm. Is that also correct?
I set time2 so that ntpd synchronizes faster in the beginning right? Should I set time1 - how? I didn't get that point out of the documentation.