Hello, I believe ntp is syncing to NMEA messages and not my PPS. I have some specific questions below.
Facts: 1. My kernel is patched to support LinuxPPS 2. ntpd-4.2.4 patched to support LinuxPPS http://ftp.enneenne.com/pub/misc/linuxpps/refclocks/nmea/ 3. I am using a Garmin GPS18 LVC with PPS tied to DCD 4. ntpd was configured with --disable-all-clocks --disable-parse-clocks --enable-NMEA --enable-LOCAL-CLOCK 5. ntp.conf contains: server 127.127.20.0 minpoll 4 prefer server 127.127.20.0 flag3 1 flag2 0 6. PPS signals are received by the kernel evidenced by entries in /var/log/messages: Jan 24 16:57:04 gps kernel: [ 136.314349] PPS event at 4294902783 Jan 24 16:57:05 gps kernel: [ 136.947295] PPS event at 4294903033 7. The NMEA clock is offset from a stratum 2 server by 600ms: r...@gps:~/ntp-4.2.4p6# ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== europium.canoni 193.79.237.14 2 u 13 64 1 154.790 548.684 0.001 GPS_NMEA(0) .GPS. 0 l 11 16 1 0.000 -63.337 0.001 8. ntpdc -c kern makes no reference to pps: r...@gps:~/ntp-4.2.4p6# ntpdc -c kern pll offset: -0.017965 s pll frequency: 82.619 ppm maximum error: 0.012304 s estimated error: 1.6e-05 s status: 0040 unsync pll time constant: 4 precision: 1e-06 s frequency tolerance: 512 ppm r...@gps:~/ntp-4.2.4p6# 9. According to ntpdc_ops.c, the pps variables are displayed only if ik_shift evaluates to true. Questions: a) Why doesn't ik_shift evaluate to true in ntpdc_ops.c? b) How can I confirm that ntp is aware of my PPS signal? c) How can I get ntp to use PPS? Thank you, Chris _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
