[gpsd-users] PPS sync troubles

[Steve Bourland]

Hoping someone has some insight into my troubles here.  Trying to use gpsd 
as my time source for ntpd.  I have two machines, one works flawlessly, 
one can not get the PPS to sync.  Same motherboards in both, using the 
same GPS (Garmin 18x LVC) connected to the "same" serial port on the 
motherboards (swapping from one machine to the other to limit variations). 
Working machine running Ubuntu kernel 3.5.0-37, non-working running Ubuntu 
kernel 3.8.0-35.  Both running ntpd version 4.2.6p3 and gpsd version 3.4 
(with -D 5 option).

Before the long list of log info, it looks like the "non-working" machine 
(lara) is giving up on the PPS after two seconds.  It reports negative 
durations with make no sense to me (and would make me throw it out also). 
As I said, the same GPS is simply being unplugged from one machine and 
plugged into the second machine.  Even stranger, I have two other machines 
with the same motherboard, one works, one doesn't.  I am stumped as to 
what to look for next to get the machines to behave consistenly (I have 
tried running the 3.5.0-37 kernel on lara to no avail).

Any suggestions or tests that need to be run are certainly appreciated as 
I am simply out of ideas at this point.
                                        Thanks,
                                          Steve


grep gpsd /var/log/syslog | grep PPS | grep -v DATA  non-working machine:

Apr 28 14:00:00 lara gpsd[9659]: gpsd:PROG: PPS Create Thread 
gpsd_ppsmonitor
Apr 28 14:00:00 lara gpsd[9659]: gpsd:PROG: PPS chrony socket 
/var/run/chrony.ttyS0.sock doesn't exist
Apr 28 14:00:00 lara gpsd[9659]: gpsd:INFO: PPS cycle: -333521267, 
duration: -333521267 @ 1398711600.995981
Apr 28 14:00:01 lara gpsd[9659]: gpsd:INFO: PPS cycle: 1000012, duration: 
0 @ 1398711601.995993
Apr 28 14:00:02 lara gpsd[9659]: gpsd:INFO: PPS cycle: -332300894, 
duration:  220361 @ 1398711602.216354
Apr 28 14:00:02 lara gpsd[9659]: gpsd:INFO: PPS cycle:  999992, duration: 
779631 @ 1398711602.995985
Apr 28 14:12:23 lara gpsd[9659]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|SPEED|TRACK|MODE|PACKET|CLEAR|PPSTIME} with reliable 
cycle detection
Apr 28 14:12:23 lara gpsd[9659]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|ALTITUDE|STATUS|MODE|PACKET|REPORT|PPSTIME} with 
reliable cycle detection
Apr 28 14:12:24 lara gpsd[9659]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|SPEED|TRACK|MODE|PACKET|CLEAR|PPSTIME} with reliable 
cycle detection
Apr 28 14:12:24 lara gpsd[9659]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|ALTITUDE|STATUS|MODE|PACKET|REPORT|PPSTIME} with 
reliable cycle detection

<the PROG lines repreat every second>

Second instance on non-working machine:

Apr 28 14:37:27 lara gpsd[21309]: gpsd:PROG: PPS Create Thread 
gpsd_ppsmonitor
Apr 28 14:37:27 lara gpsd[21309]: gpsd:PROG: PPS chrony socket 
/var/run/chrony.ttyS0.sock doesn't exist
Apr 28 14:37:27 lara gpsd[21309]: gpsd:PROG: PPS thread awaiting device 
activation
Apr 28 14:40:26 lara gpsd[21309]: gpsd:INFO: PPS cycle: 2092237334, 
duration: 2092237334 @ 1398714026.754582
Apr 28 14:41:27 lara gpsd[21309]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|SPEED|TRACK|MODE|PACKET|CLEAR|PPSTIME} with reliable 
cycle detection
Apr 28 14:41:27 lara gpsd[21309]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|ALTITUDE|STATUS|MODE|PACKET|REPORT|PPSTIME} with 
reliable cycle detection
Apr 28 14:41:28 lara gpsd[21309]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|SPEED|TRACK|MODE|PACKET|CLEAR|PPSTIME} with reliable 
cycle detection
Apr 28 14:41:28 lara gpsd[21309]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|ALTITUDE|STATUS|MODE|PACKET|REPORT|PPSTIME} with 
reliable cycle detection
Apr 28 14:41:29 lara gpsd[21309]: gpsd:PROG: Changed mask: 
{ONLINE|TIME|LATLON|SPEED|TRACK|MODE|PACKET|CLEAR|PPSTIME} with reliable 
cycle detection



Working machine:

Apr 28 14:13:36 lois gpsd[25639]: gpsd:PROG: PPS Create Thread 
gpsd_ppsmonitor
Apr 28 14:13:36 lois gpsd[25639]: gpsd:PROG: PPS chrony socket 
/var/run/chrony.ttyS0.sock doesn't exist
Apr 28 14:13:36 lois gpsd[25639]: gpsd:PROG: PPS thread awaiting device 
activation
Apr 28 14:18:19 lois gpsd[25639]: gpsd:INFO: PPS cycle: 765458732, 
duration: 765458732 @ 1398712699.975980
Apr 28 14:18:20 lois gpsd[25639]: gpsd:INFO: PPS cycle: 765679136, 
duration:  220404 @ 1398712700.196384
Apr 28 14:18:20 lois gpsd[25639]: gpsd:INFO: PPS cycle: 1002965, duration: 
782561 @ 1398712700.978945
Apr 28 14:18:21 lois gpsd[25639]: gpsd:INFO: PPS cycle: 1002981, duration: 
220420 @ 1398712701.199365
Apr 28 14:18:22 lois gpsd[25639]: gpsd:INFO: PPS cycle: 1020995, duration: 
800575 @ 1398712701.999940
Apr 28 14:18:22 lois gpsd[25639]: gpsd:INFO: PPS cycle: 1021007, duration: 
220432 @ 1398712702.220372
Apr 28 14:18:23 lois gpsd[25639]: gpsd:INFO: PPS cycle: 2000014, duration: 
1779582 @ 1398712703.999954
Apr 28 14:18:24 lois gpsd[25639]: gpsd:INFO: PPS cycle: 1999988, duration: 
220406 @ 1398712704.220360
Apr 28 14:18:24 lois gpsd[25639]: gpsd:INFO: PPS cycle: 1000001, duration: 
779595 @ 1398712704.999955
Apr 28 14:18:25 lois gpsd[25639]: gpsd:INFO: PPS cycle:  999997, duration: 
220402 @ 1398712705.220357
Apr 28 14:18:26 lois gpsd[25639]: gpsd:INFO: PPS cycle: 1000013, duration: 
779611 @ 1398712705.999968
Apr 28 14:18:26 lois gpsd[25639]: gpsd:INFO: PPS cycle: 1000002, duration: 
220391 @ 1398712706.220359