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From: | Nick Burkitt |
Subject: | Re[2]: NTP with only GPS/PPS flags PPS as falseticker |
Date: | Thu, 19 Mar 2020 00:56:42 +0000 |
User-agent: | eM_Client/7.2.37929.0 |
If I disconnect the Ethernet cable off my Pi 3B+, NTPsec 1.1.8 continues to show the GPSd PPS shm as (+) and the PPS refclock shows (o). This is a significant difference from you, I use the Linux kernel PPS refclock as a "prefer". It's activated by a
dtoverlay=pps-gpio,gpiopin=18,assert_falling_edge=off,capture_clear=offin the Pi's config.txt file, and takes the MAX-M8Q's PPS pulse and sends it to the kernel. So, my configuration may be different enough not to help much.
Still, here's most of my ntp.conf (whole file attached):
# flag2 0 | 1 - Specifies PPS capture on the rising (assert) pulse edge if 0 (default) or falling (clear) pulse edge if 1. # flag3 0 | 1 - Controls the kernel PPS discipline: 0 for disable (default), 1 for enable. refclock pps unit 0 refid kPPS flag2 0 flag3 0 minpoll 4 prefer # time1 time - Specifies the time offset calibration factor, in seconds and fraction, with default 0.0. # flag1 0 | 1 - Skip the difference limit check if set. Useful for systems where the RTC backup cannot keep the time # over long periods without power and the SHM clock must be able to force long-distance initial jumps. Check the difference limit if cleared (default). refclock shm unit 1 refid gPPS minpoll 4 refclock shm unit 0 refid GNSS stratum 11 flag1 0 time1 0.060 # fudged so it stays positive and minimum +10ms offset
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