Pour avoir un raspberry hors ligne à l'heure :
sudo apt install gpsd gpsd-clients ntp
sudo sed -i 's|DEVICES=""|DEVICES="/dev/gps0"|' /etc/default/gpsd
sudo sed -i 's|GPSD_OPTIONS=""|GPSD_OPTIONS="-n"|' /etc/default/gpsd
sudo systemctl restart gpsd

# contrôle du GPS :
cgps -s

# NTP
echo "
# GPS Serial data reference
server 127.127.28.0 minpoll 4 maxpoll 4
fudge 127.127.28.0 time1 0.0 refid GPS

# GPS PPS reference
server 127.127.28.1 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.1 refid PPS
" | sudo tee -a /etc/ntp.conf
sudo systemctl restart ntp
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