import os
import sys
import time
from gps import *
 
print 'Attempting to access GPS time...'
 
try:
	gpsd = gps(mode=WATCH_ENABLE)
except:
	print 'No GPS connection present. TIME NOT SET.'
	sys.exit()
 
while True:
	gpsd.next()
	if gpsd.utc != None and gpsd.utc != '':
		gpstime = gpsd.utc[0:4] + gpsd.utc[5:7] + gpsd.utc[8:10] + ' ' + gpsd.utc[11:19]
		print 'Setting system time to GPS time...'
		os.system('sudo date -u --set="%s"' % gpstime)
		print 'System time set.'
		sys.exit()
	time.sleep(1)

# Welcome to the chrony configuration file. See chrony.conf(5) for more
# information about usuable directives.
pool 2.debian.pool.ntp.org iburst
 
# This directive specify the location of the file containing ID/key pairs for
# NTP authentication.
keyfile /etc/chrony/chrony.keys
 
# This directive specify the file into which chronyd will store the rate
# information.
driftfile /var/lib/chrony/chrony.drift
 
# Uncomment the following line to turn logging on.
#log tracking measurements statistics
 
# Log files location.
logdir /var/log/chrony
 
# Stop bad estimates upsetting machine clock.
maxupdateskew 100.0
 
# This directive enables kernel synchronisation (every 11 minutes) of the
# real-time clock. Note that it can’t be used along with the 'rtcfile' directive.
rtcsync
 
# Step the system clock instead of slewing it if the adjustment is larger than
# one second, but only in the first three clock updates.
makestep 1 3
refclock SHM 0 offset 0.5 delay 0.2 refid GPS