[SOLVED] Serial GPS NTP Displays Incorrect Source on Dashboard

[stephenw10]

The jitter there seems high for something with PPS. I expect to see <0.01ms as you showed earlier.

You can see the offset is still larger than some remote servers so ntpd is using those. You probably need to adjust the fudgetime2 value to bring it down.

Unfortunately my own gps failed a while ago when my cat destroyed the antenna so I only have old data to refer to like this:

[2.5.0-DEVELOPMENT][root@2220.stevew.lan]/root: ntpq -c cv
associd=0 status=0021 2 events, clk_no_reply,
device="NMEA GPS Clock",
timecode="$GPGGA,190002.000,xxxx.xxxx,N,xxxx.xxxx,W,2,10,1.13,97.4,M,47.0,M,0000,0000*4D",
poll=49689, noreply=1, badformat=1, baddata=0, fudgetime2=550.000,
stratum=0, refid=GPS, flags=7

[2.5.0-DEVELOPMENT][root@2220.stevew.lan]/root: ntpq -c pe
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
oGPS_NMEA(0)     .GPS.            0 l    6   16  377    0.000   -0.006   0.001
 0.pfsense.pool. .POOL.          16 p    -   64    0    0.000    0.000   0.000
-213.251.53.217  193.0.0.229      2 u   56   64  277    6.824   -0.226   0.348
+85.199.214.100  .GPS.            1 u   11   64  177    7.250   -0.056   0.403
-time.videxio.ne 131.188.3.223    2 u   16   64  177    6.508   -0.393   0.235
-x.ns.gin.ntt.ne 249.224.99.213   2 u   19   64   27    5.535    0.231   0.323
+185.121.25.166  85.199.214.98    2 u   52   64  377    6.815   -0.140   0.326
-time.shf.uk.as4 129.250.35.250   3 u   22   64   77    9.020    1.393   0.185
+bronze.netweave 85.199.214.98    2 u   56   64  377    8.020   -0.126   0.156
+195.195.221.100 .GPS.            1 u    1   64  377   16.141    0.014   0.227

I do have a USB GPS which works fine but has no PPS:

[23.01-RELEASE][admin@fw1.stevew.lan]/root: ntpq -c pe
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*GPS_NMEA(0)     .GPS.            0 l    3   16  377    0.000   -2.347   1.895
 0.pfsense.pool. .POOL.          16 p    -   64    0    0.000   +0.000   0.001
-79-209.butt.spd 51.155.213.242   2 u   33  128  377   12.146  +24.507  10.064
+85.199.214.100  .GPS.            1 u  144   64  364    7.314  +23.577   1.440
+ntp.nat.ms      195.66.241.3     2 u   53   64  377   18.178  +25.346   1.021

And hence bad jitter!

[Dobby_]

If I block outbound pools, it seems to sync and will report .GPS. (stratum 0, PPS)

In one of your pictures shown above you may be able to read something like, "Satellites in usage 8" (number of connected satellites)" so your gps is using that satellites
for grabbing time from.

Please see at the red arrow.

[elvisimprsntr]

@stephenw10

Here is the best write up I have read why there is an offset between the NMEA messages and PPS signal, and how to adjust the fudge 2 time to compensate for that difference. I am assuming the explanation is the same for the 16x and 18x.

https://support.ntp.org/Support/ConfiguringNMEARefclocks#Section_6.1.12.2

Obviously, one needs to infer the example ntp.conf settings to the fields in pfSense Serial GPS options. I am going to give it a try and see how well it works in practice.

[elvisimprsntr]

@elvisimprsntr

BACKGROUND

I used the procedure at the following link to calibrate the NMEA messages vs PPS signal fudge 2 time. I also eliminated a 10' Cat5e extension cable with the hope of reducing the PPS jitter.

https://support.ntp.org/Support/ConfiguringNMEARefclocks#Section_6.1.12.2

SETTINGS

Baud Rate: 38400
NMEA Messages: GPGGA only
Fudge 1: 0.0
Fudge 2: 0.369

RESULTS

I am still getting some PPS sync error messages, but I think that is because the 16x is skipping some messages. I don't think it's a wiring quality or length issue.

Apr 13 14:02:30 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 14:05:58 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 14:32:22 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:22:30 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:30:46 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:39:50 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:47:34 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:56:06 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:57:42 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded



cat /dev/gps0 

$GPGGA,[REDACTED],N,08007.2503,W,1,08,1.0,18.6,M,-28.7,M,,*48
$GPGGA,[REDACTED],N,08007.2503,W,1,08,1.0,18.6,M,-28.7,M,,*46
$GPGGA,[REDACTED],N,08007.2502,W,1,08,1.0,18.6,M,-28.7,M,,*45
$GPGGA,[REDACTED],N,08007.2502,W,1,08,1.0,18.6,M,-28.7,M,,*49
$GPGGA,[REDACTED],N,08007.2502,W,1,08,1.0,18.5,M,-28.7,M,,*43
$GPGGA,[REDACTED],N,08007.2503,W,1,08,1.0,18.5,M,-28.7,M,,*49
 <- blank LF here
$GPGGA,[REDACTED],N,08007.2505,W,1,08,1.0,18.5,M,-28.7,M,,*4C
$GPGGA,[REDACTED],N,08007.2505,W,1,08,1.0,18.4,M,-28.7,M,,*48
$GPGGA,[REDACTED],N,08007.2504,W,1,08,1.0,18.4,M,-28.7,M,,*41
$GPGGA,[REDACTED],N,08007.2504,W,1,08,1.0,18.4,M,-28.7,M,,*42

[stephenw10]

Mmm, looks better though.

[elvisimprsntr]

For anyone who needs a Stratum 0 GPS+PPS source connected to pfSense, I have tested three different models of Garmin GPS receivers connected to appliances with a full DE9 RS232 port (PPS on DCD pin 1) and RJ45 COM port (PPS on CTS pin 8). Achieves less than 10 usec offset/jitter for less than $50 off evilBay.

Instructions

Garmin models tested:

• GPS 16X LVS
• GPS 18X LVC
• GPS 19X HVS

[stephenw10]

Nice write up!

[ccb056]

@elvisimprsntr said in [SOLVED] Serial GPS NTP Displays Incorrect Source on Dashboard:

@elvisimprsntr
I am still getting some PPS sync error messages, but I think that is because the 16x is skipping some messages. I don't think it's a wiring quality or length issue.

Apr 13 14:02:30 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 14:05:58 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 14:32:22 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:22:30 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:30:46 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:39:50 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:47:34 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:56:06 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Apr 13 15:57:42 ntp ntpd[12395]: kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded

Have you been able to determine the source of the PPS Jitter exceeded error?
I've had the same error for years on my old setup (Garmin 18x LVC + Dell Optiplex)

What voltage is your PPS signal? ~3.5 volts?

I've recently started trying to migrate to a new N100 box off ebay, shipped from China, and I'm having the hardest time trying to get the Garmin 18x LVC setup working. Sometimes the NMEA sentences will come through for the first 1-2 minutes after boot, and then they stop.

Same exact setup was working fine in the Dell Optiplex

Not sure if it's due to the TTL output levels on the Garmin and the sensitivity of the RS-232 port on the PC?

[elvisimprsntr]

@ccb056 I still get the PPS jitter errors, just not as frequent. Doesn't seem to affect PPS synchronization.

Jul 12 15:54:26	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 11 19:40:42	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 11 10:37:14	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 11 02:35:22	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 11 02:09:06	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 11 00:40:02	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 10 19:40:10	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 9 23:17:22	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 9 21:42:42	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 9 11:08:02	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 9 10:56:42	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 9 09:53:38	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded
Jul 9 09:41:46	ntpd	30926	kernel reports TIME_ERROR: 0x2307: PPS Time Sync wanted but PPS Jitter exceeded

Not sure if it is related the Garmin pucks occasionally skipping NMEA messages. Per Garmin Tech Support, this is expected behavior.

cat /dev/gps0 
$GPGGA,001849,XXXX.5745,N,08007.2564,W,1,10,0.9,35.5,M,-28.7,M,,*44
$GPGGA,001850,XXXX.5745,N,08007.2564,W,1,10,0.9,35.5,M,-28.7,M,,*4C
$GPGGA,001851,XXXX.5746,N,08007.2564,W,1,10,0.9,35.6,M,-28.7,M,,*4D
$GPGGA,001852,XXXX.5746,N,08007.2564,W,1,10,0.9,35.7,M,-28.7,M,,*4F
$GPGGA,001853,XXXX.5747,N,08007.2564,W,1,10,0.9,35.8,M,-28.7,M,,*40

$GPGGA,001855,XXXX.5747,N,08007.2564,W,1,09,1.0,36.0,M,-28.7,M,,*4D
$GPGGA,001856,XXXX.5748,N,08007.2564,W,1,09,1.0,36.0,M,-28.7,M,,*41
$GPGGA,001857,XXXX.5748,N,08007.2564,W,1,09,1.0,36.1,M,-28.7,M,,*41

$GPGGA,001858,XXXX.5749,N,08007.2564,W,1,09,1.0,36.2,M,-28.7,M,,*4C
$GPGGA,001859,XXXX.5749,N,08007.2564,W,1,09,1.0,36.3,M,-28.7,M,,*4C
$GPGGA,001900,XXXX.5750,N,08007.2564,W,1,09,1.0,36.3,M,-28.7,M,,*49

$GPGGA,001902,XXXX.5751,N,08007.2563,W,1,09,1.0,36.5,M,-28.7,M,,*4B
$GPGGA,001903,XXXX.5751,N,08007.2563,W,1,09,1.0,36.6,M,-28.7,M,,*49

$GPGGA,001904,XXXX.5751,N,08007.2563,W,1,09,1.0,36.6,M,-28.7,M,,*4E

[dennypage]

@elvisimprsntr said in [SOLVED] Serial GPS NTP Displays Incorrect Source on Dashboard:

Not sure if it is related the Garmin pucks occasionally skipping NMEA messages. Per Garmin Tech Support, this is expected behavior.

Doesn't seem right to me. While skipping sentences might be okay for navigation, it isn't okay for timekeeping. If Garmin says that's expected, you should get a different receiver.

[elvisimprsntr]

@dennypage Hasn't been a problem.