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    [SOLVED] Serial GPS NTP Displays Incorrect Source on Dashboard

    General pfSense Questions
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    • E
      elvisimprsntr
      last edited by elvisimprsntr

      BACKGROUND

      I am running CE on my primary Protectli Vault, which unfortunately does not have a DE9 RS232 port with the DCD pin required for the PPS signal. So, I picked up a used fanless Qotom computer, installed pfSense, and connected my Garmin GPS 16x LVS to one of the RS232 ports.

      PFSENSE NTP SERVER CONFIG

      I configured the dedicated pfSense NTP server to prefer the GPS source and added a time.nist.gov pool. The best I can tell the NTP server is actually using the GPS source, but one of the NIST servers is marked as the active peer on both the NTP status and dashboard.

      Screenshot 2023-04-11 at 9.04.59 AM.png

      Screenshot 2023-04-11 at 9.03.16 AM.png

      Screenshot 2023-04-11 at 9.05.36 AM.png

      PRIMARY PFSENSE FIREWALL CONFIG

      On my primary pfSense firewall, I added my GPS NTP server and a time.nist.gov pool, which both the NTP status and dashboard are showing that it is receiving time from my GPS NTP source.

      Screenshot 2023-04-11 at 9.06.20 AM.png

      Screenshot 2023-04-11 at 9.06.07 AM.png

      Screenshot 2023-04-11 at 9.05.58 AM.png

      Screenshot 2023-04-11 at 9.06.58 AM.png

      QUESTION

      I think I have everything configured per intent, and the best I can tell both the NTP server and my firewall are both using my GPS as the source.

      But why does my NTP server report one of the servers in the NIST pool as the active peer?

      Is it using the NIST server as the time source and only the PPS signal from the GPS to synchronize time?

      Thanks in advance,

      Elvis

      JKnottJ E 2 Replies Last reply Reply Quote 0
      • JKnottJ
        JKnott @elvisimprsntr
        last edited by

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

        which unfortunately does not have a DB9 DE-9 RS232

        There's no such thing as a "DB9"

        But why does my NTP server report one of the servers in the NIST pool as the active peer?

        My understanding is all sources are used as peers, with different weights applied according to stratum. In addition to providing redundancy, it also improves accuracy.

        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...

        E 1 Reply Last reply Reply Quote 1
        • E
          elvisimprsntr @JKnott
          last edited by elvisimprsntr

          @jknott

          From your signature:

          "PfSense running on Qotom mini PC"

          Which model specifically and does it have a DE-9 ๐Ÿ˜† RS232 port?

          JKnottJ 1 Reply Last reply Reply Quote 0
          • 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...

            1 Reply Last reply Reply Quote 0
            • 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

              E 1 Reply Last reply Reply Quote 0
              • 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.

                1 Reply Last reply Reply Quote 0
                • 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?

                  E 1 Reply Last reply Reply Quote 0
                  • 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
                    
                    
                    
                    1 Reply Last reply Reply Quote 0
                    • 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!

                      E 1 Reply Last reply Reply Quote 0
                      • 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.

                          E 1 Reply Last reply Reply Quote 0
                          • 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
                            
                            
                            
                            1 Reply Last reply Reply Quote 0
                            • stephenw10S
                              stephenw10 Netgate Administrator
                              last edited by

                              Mmm, looks better though.

                              1 Reply Last reply Reply Quote 0
                              • 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
                                1 Reply Last reply Reply Quote 2
                                • stephenw10S
                                  stephenw10 Netgate Administrator
                                  last edited by

                                  Nice write up! ๐Ÿ‘

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