galmon: ntp with nmea and pps

99-pps.rules

KERNEL=="ttyS0", SYMLINK+="gps0"
KERNEL=="pps0", OWNER="root", GROUP="dialout", MODE="0660"

README.md

Based on https://www.ardusimple.com/product/simplertk2b-pro/ hooked up to rpi3 via https://www.ardusimple.com/product/raspberry-adapter-for-simplertk2b/
Use USB cable from gps to rpi, this becomes ttyACM0 and is used by ubxtool.
The rpi uart is ttyS0 and symlinked to /dev/gps0

config.txt

dtoverlay=pps-gpio,gpiopin=11
enable_uart=1
# make sure to disable console on serial in raspi-config
# sudo systemctl disable hciuart

ntp.conf

# only the important rows included, logs etc you can leave as is.

tos mindist 0.4 # allows pps to kick in

server 127.127.20.0 mode 48 minpoll 4 maxpoll 5 prefer # 38k4 parse RMC
fudge 127.127.20.0 stratum 10
fudge 127.127.20.0 time2 0.110 # NMEA offset, not critical

server 127.127.22.0 minpoll 4 maxpoll 5

pool 0.pool.ntp.org noselect

ntpq -p; ntptime

     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*GPS_NMEA(0)     .GPS.           10 l    2   16  377    0.000   +2.755   3.435
oPPS(0)          .PPS.            0 l   26   32  377    0.000   -0.002   0.002
 0.se.pool.ntp.o .POOL.          16 p    -   64    0    0.000   +0.000   0.002
 192.168.1.255   .BCST.          16 B    -   64    0    0.000   +0.000   0.002
 lul2.ntp.netnod .PPS.            1 u    2   64  377   21.936   -0.158   0.075
 ntp2.vmar.se    194.58.202.148   2 u    6   64  377   10.459   -0.001   0.088
 svl2.ntp.netnod .PPS.            1 u    4   64  377   15.412   -0.181   0.065
 sth2.ntp.netnod .PPS.            1 u   60   64  377   10.378   -0.102   0.073
 mmo1.ntp.netnod .PPS.            1 u    5   64  377   17.988   +0.044   0.045
 ntp3.flashdance 192.36.143.153   2 u    2   64  377   11.039   +0.114   0.263
 ntp-c.0x5e.se   194.58.204.148   2 u   59   64    3   18.776   +0.062   0.053
 mmo2.ntp.netnod .PPS.            1 u   55   64    3   17.536   -0.037   0.044
 time.cloudflare 10.128.9.203     3 u   54   64    3    9.940   -0.142   0.116

ntp_gettime() returns code 0 (OK)
  time e694c319.cdd8c6d8  Wed, Aug  3 2022 11:49:13.804, (.804089654),
  maximum error 413000 us, estimated error 2 us, TAI offset 37
ntp_adjtime() returns code 0 (OK)
  modes 0x0 (),
  offset -1.865 us, frequency -4.352 ppm, interval 1 s,
  maximum error 413000 us, estimated error 2 us,
  status 0x2001 (PLL,NANO),
  time constant 5, precision 0.001 us, tolerance 500 ppm,

uart1-ntp.txt

# Config changes format version 1.0
# created by u-center version 22.05 at 18:42:59 on Tuesday, 02 Aug 2022
[del]
[set]
Flash CFG-UART1OUTPROT-UBX 0                    # write value 0                    to item id 0x10740001 in layer 2
Flash CFG-MSGOUT-NMEA_ID_GGA_UART1 0x0                  # write value 0  0x0               to item id 0x209100bb in lay
Flash CFG-MSGOUT-NMEA_ID_GLL_UART1 0x0                  # write value 0  0x0               to item id 0x209100ca in lay
Flash CFG-MSGOUT-NMEA_ID_GSA_UART1 0x0                  # write value 0  0x0               to item id 0x209100c0 in lay
Flash CFG-MSGOUT-NMEA_ID_GSV_UART1 0x0                  # write value 0  0x0               to item id 0x209100c5 in lay
Flash CFG-MSGOUT-NMEA_ID_VTG_UART1 0x0                  # write value 0  0x0               to item id 0x209100b1 in lay