macOS - BYO-NTP/recipes GitHub Wiki

1. macOS has no official PPS support, so 3e-3 is as good as we can get with a refclock. I tested mac-pps and it improves accuracy to within 3e-4.
2. there's no udev or devfs equivalent on macOS, so ntp drivers such as NMEA and GPSD-NG that have hard coded paths to /dev/gps0 don't work.
3. NTPsec has improved that by adding a path option, so it has more refclock options available. I can think of no reason to prefer the legacy ntp over NTPsec.
4. Chrony accuracy is much better than ntp and NTPsec. Chrony has some great knobs to twiddle (poll, minsamples) that can smooth out the USB-induced latency.

If it doesn't already have a USB port, wire the GNSS to a USB to serial TTL adapter. Connect the assembly to a Windows computer with u-blox u-center installed. I run Windows under VMware Fusion and it works well. Configure the GNSS per the recommendations on the gnss page.

export NTP_REFCLOCKS=$(cat <<EO_NTPSEC_NMEA
refclock SHM 0 refid NMEA precision 0.02 poll 2 offset 0.06 prefer trust
EO_NTPSEC_NMEA
)
curl -sS https://byo-ntp.github.io/tools/chrony/install.sh | sudo -E sh

NTPsec, using the NMEA driver:

export NTP_REFCLOCKS=$(cat <<EO_NTPSEC_NMEA
refclock nmea path /dev/cu.usbmodem1101 minpoll 3 maxpoll 4 time2 0.06 baud 115200 prefer
EO_NTPSEC_NMEA
)
curl -sS https://byo-ntp.github.io/tools/ntpsec/install.sh | sudo -E sh

NTPsec, using gpsd and the SHM driver:

export NTP_REFCLOCKS=$(cat <<EO_NTPSEC_SHM
refclock shm unit 0 refid NMEA minpoll 3 maxpoll 4 time1 0.06
EO_NTPSEC_SHM
)
curl -sS https://byo-ntp.github.io/tools/ntpsec/install.sh | sudo -E sh

NTPsec, using gpsd and the gpsd JSON driver:

export NTP_REFCLOCKS=$(cat <<EO_NTPSEC_JSON
refclock gpsd path /dev/cu.usbmodem1101 refid NMEA minpoll 3 maxpoll 4 time2 0.06 prefer
EO_NTPSEC_JSON
)
curl -sS https://byo-ntp.github.io/tools/ntpsec/install.sh | sudo -E sh

ntp, using gpsd via the SHM driver.

export NTP_REFCLOCKS=$(cat <<EO_NTP
server 127.127.28.2 minpoll 3 maxpoll 4 prefer
fudge  127.127.28.2 refid NMEA time1 0.06 minjitter 0.03
EO_NTP
)
curl -sS https://byo-ntp.github.io/tools/ntp/install.sh | sudo -E sh

• watch the status in near real time:
  • sudo port install watch
  • printf '\e[8;9;80t'; watch -n2 chronyc sources
  • printf '\e[8;9;80t'; watch -n2 ntpq -c peer
• Measure the offset
• Gather statistics with telegraf + influxdb + grafana or similar.

• mac-pps, issue #1, results
• Jeff Geerling, Using GPS...on a Mac

Chrony

NTPsec, NMEA

NTPsec, GPSD