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    [SOLVED] Serial GPS NTP Displays Incorrect Source on Dashboard

    General pfSense Questions
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    • JKnottJ
      JKnott @elvisimprsntr
      last edited by

      @elvisimprsntr

      I've forgotten the model, but it does have the DE-9 serial port.

      PfSense running on Qotom mini PC
      i5 CPU, 4 GB memory, 32 GB SSD & 4 Intel Gb Ethernet ports.
      UniFi AC-Lite access point

      I haven't lost my mind. It's around here...somewhere...

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      • stephenw10S
        stephenw10 Netgate Administrator
        last edited by stephenw10

        You could be using GPS for the PPS signal but not actual time value. That fine as long as you don't lose access to external ntp servers. If you need to be able to sync to GPS only you need a GPS peer configured not just a PPS.
        There are two tabs on the NTP settings. The PPS tab is usually not used for a GPS source since PPS is enabled on the GPS tab by default.

        Steve

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        • E
          elvisimprsntr @stephenw10
          last edited by

          @stephenw10 said in Serial GPS NTP Displays Incorrect Source on Dashboard:

          There are two tabs on the NTP settings. The PPS tab is usually not used for a GPS source since PPS is enabled on the GPS tab by default.

          That's what I have enabled. PPS on the Serial GPS tab and not the separate PPS tab.

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          • stephenw10S
            stephenw10 Netgate Administrator
            last edited by

            Ok, then you may need to tweak the fudge values so the offset is low enough.

            ntp is a fickle beast though! It might just appear to be doing that. Try not configuring any external servers. Does it still sync?

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            • E
              elvisimprsntr @stephenw10
              last edited by elvisimprsntr

              @stephenw10

              This is the output I see. What do I need to tweak?

              [2.6.0-RELEASE][root@redacted]/root: ntpq -c kerninfo
              associd=0 status=041d leap_none, sync_uhf_radio, 1 event, kern,
              pll offset:            -1.4569
              pll frequency:         -20.8333
              maximum error:         9.857
              estimated error:       0.032
              kernel status:         pll ppsfreq ppstime ppssignal nano
              pll time constant:     4
              precision:             1e-06
              frequency tolerance:   495.911
              pps frequency:         -20.8333
              pps stability:         4.87634
              pps jitter:            0.011
              calibration interval   256
              calibration cycles:    41
              jitter exceeded:       46
              stability exceeded:    0
              calibration errors:    5
              [2.6.0-RELEASE][root@redaced]/root: ntptime
              ntp_gettime() returns code 0 (OK)
                time e7e0825d.fc0a6b94  Tue, Apr 11 2023 21:05:33.984, (.984534236),
                maximum error 3222 us, estimated error 42 us, TAI offset 0
              ntp_adjtime() returns code 0 (OK)
                modes 0x0 (),
                offset -1440.389 us, frequency -20.833 ppm, interval 256 s,
                maximum error 3222 us, estimated error 42 us,
                status 0x2107 (PLL,PPSFREQ,PPSTIME,PPSSIGNAL,NANO),
                time constant 4, precision 0.001 us, tolerance 496 ppm,
                pps frequency -20.833 ppm, stability 4.876 ppm, jitter 11.503 us,
                intervals 41, jitter exceeded 46, stability exceeded 0, errors 5.
              [2.6.0-RELEASE][root@redacted]/root: ntpq -p
                   remote           refid      st t when poll reach   delay   offset  jitter
              ==============================================================================
              oGPS_NMEA(0)     .GPS.            0 l    7   16  377    0.000   -1.476   0.508
               time.nist.gov   .POOL.          16 p    -   64    0    0.000   +0.000   0.000
              +utcnist2.colora .NIST.           1 u   22   64  377   55.943   +0.397   1.938
              *time-e-wwv.nist .NIST.           1 u   25   64  377   54.777   +0.032   1.944
              +time-e-b.nist.g .NIST.           1 u   22   64   77   50.584   -2.255   0.752
              
              

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

              [2.6.0-RELEASE][root@redacted]/root: ntpq -c kerninfo
              associd=0 status=041d leap_none, sync_uhf_radio, 1 event, kern,
              pll offset:            -0.261249
              pll frequency:         -20.7932
              maximum error:         6.5
              estimated error:       0.008
              kernel status:         pll ppsfreq ppstime ppssignal nano
              pll time constant:     4
              precision:             1e-06
              frequency tolerance:   495.911
              pps frequency:         -20.7932
              pps stability:         4.64194
              pps jitter:            0.003
              calibration interval   256
              calibration cycles:    46
              jitter exceeded:       50
              stability exceeded:    0
              calibration errors:    6
              [2.6.0-RELEASE][root@redacted]/root: ntptime
              ntp_gettime() returns code 0 (OK)
                time e7e087e2.c4db2704  Tue, Apr 11 2023 21:29:06.768, (.768969647),
                maximum error 4000 us, estimated error 5 us, TAI offset 0
              ntp_adjtime() returns code 0 (OK)
                modes 0x0 (),
                offset -221.215 us, frequency -20.793 ppm, interval 256 s,
                maximum error 4000 us, estimated error 5 us,
                status 0x2107 (PLL,PPSFREQ,PPSTIME,PPSSIGNAL,NANO),
                time constant 4, precision 0.001 us, tolerance 496 ppm,
                pps frequency -20.793 ppm, stability 4.642 ppm, jitter 3.252 us,
                intervals 46, jitter exceeded 51, stability exceeded 0, errors 6.
              [2.6.0-RELEASE][root@redacted]/root: ntpq -p
                   remote           refid      st t when poll reach   delay   offset  jitter
              ==============================================================================
              oGPS_NMEA(0)     .GPS.            0 l   11   16  377    0.000   -0.204   0.070
               time.nist.gov   .POOL.          16 p    -   64    0    0.000   +0.000   0.000
               time-a-wwv.nist (loop)           2 u  137   64  234    0.163   -0.968   1.053
               time-e-wwv.nist (loop)           2 u    3   64  143    0.140   -0.114   0.545
              
              
              
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              • stephenw10S
                stephenw10 Netgate Administrator
                last edited by

                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 ๐Ÿ™„ 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!

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                • Dobby_D
                  Dobby_
                  last edited by

                  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.

                  ntp source.jpg

                  Please see at the red arrow.

                  #~. @Dobby

                  Turris Omnia - 4 Ports - 2 GB RAM / TurrisOS 7 Release (Btrfs)
                  PC Engines APU4D4 - 4 Ports - 4 GB RAM / pfSense CE 2.7.2 Release (ZFS)
                  PC Engines APU6B4 - 4 Ports - 4 GB RAM / pfSense+ (Plus) 24.03_1 Release (ZFS)

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                  • E
                    elvisimprsntr @stephenw10
                    last edited by 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.

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                    • E
                      elvisimprsntr @elvisimprsntr
                      last edited by 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

                      Screenshot 2023-04-13 at 3.43.32 PM.png

                      RESULTS

                      Screenshot 2023-04-13 at 3.40.27 PM.png

                      Screenshot 2023-04-13 at 3.40.58 PM.png

                      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
                      
                      
                      
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                      • stephenw10S
                        stephenw10 Netgate Administrator
                        last edited by

                        Mmm, looks better though.

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                        • E
                          elvisimprsntr @elvisimprsntr
                          last edited by 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
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                          • stephenw10S
                            stephenw10 Netgate Administrator
                            last edited by

                            Nice write up! ๐Ÿ‘

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