Configuring the time server

Recommended (optional) steps: setting up the hardware device names

For the ADAPT payload software, we use /dev/gps and /dev/spatial as names for the NMEA and Advanced Navigation Spatial hardware names (this avoids issues with ttyUSB0/1/2 etc. numbering). In order to set this up, you'll need to know the device IDs - usually found with the 'lsusb' command. For reference, the USB hardware we used look like this:

lsusb
067b:2303 Prolific Technology, Inc. PL2303 Serial Port   # <- this is the 9-pin serial to USB converter
0403:6001 Future Technology Devices International, Ltd FT232 USB-Serial (UART) IC  # <- this is the standard Spatial USB cable

Setup the udev rule

sudo nano /etc/udev/rules.d/99-zgps.rules
# copy and paste the info below (after changing the IDs to match your hardware)

/etc/udev/rules.d/99-zgps.rules

SUBSYSTEM=="tty", ATTRS{idVendor}=="067b", ATTRS{idProduct}=="2303", GROUP="dialout",  SYMLINK+="gps"
SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", GROUP="dialout", SYMLINK+="spatial"

Reload the udev rules to see /dev/gps and /dev/spatial

udevadm control --reload-rules && udevadm trigger

Required steps: configuring gpsd and chronyd

Disable the standard timesync

sudo systemctl stop systemd-timesyncd.service
sudo systemctl disable systemd-timesyncd.service

Disable standard gpsd startup since we may need to run it in debug mode

sudo systemctl stop gpsd
sudo systemctl disable gpsd
sudo systemctl stop gpsd.socket
sudo systemctl disable gpsd.socket

If you do need to run it in debug mode, issue these commands to test it and see output

sudo killall gpsd
sudo gpsd -D 5 -N -n -b /dev/gps /dev/pps0

note: the ADAPT payload software will start gpsd (refer to this for reference)

Configure chrony

sudo systemctl stop chronyd
sudo nano /etc/chrony/chrony.conf
# add/edit lines as shown below

/etc/chrony/chrony.conf

allow
# rtcsync  # note: turn this off to not use system clock
refclock SHM 0 refid GPS precision 1e-1 offset 0.045 noselect
refclock SHM 2 refid PPS precision 1e-7 prefer

Start chrony and review the sources

sudo systemctl start chronyd
chronyc sources

we want the PPS and GPS to show like this:

MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
#- GPS                           0   4   377    12  +3580us[+3580us] +/- 101ms
#* PPS                           0   4   377    10    -86ns[ -157ns] +/- 181ns

Note: the * next to PPS

Next Step