set-systime-from-gps.py

#!/usr/bin/env python

import sys, subprocess

def get_gps_datetime():
    timestamp = ''
    date = ''
    datastream = open('/dev/serial/by-id/usb-Silicon_Labs_CP2102_USB_to_UART_Bridge_Controller_0001-if00-port0','r')
    for line in datastream :
        if line.startswith( '$GPZDA' ) :
            # extract time
            time_stamp = get_formatted_time(line)
            # extract date
            date_stamp = get_formatted_date(line)
            break
    return date_stamp+' '+time_stamp

def get_formatted_time(str):
    time = str.strip().split(',')[1]
    return time[:2]+':'+time[2:4]+':'+time[4:6]

def get_formatted_date(str):
    day = str.strip().split(',')[2]
    month = str.strip().split(',')[3]
    year = str.strip().split(',')[4]
    return year+'-'+month+'-'+day

def set_time(str):
    print("date time is {}".format(str))
#    os.system('sudo date -s %s' % str)
    try:
        subprocess.check_call(['timedatectl','set-ntp','false'])
    except subprocess.CalledProcessError:
        error_out("timedatectl execution failed: {0}".format(e))

    try:
        subprocess.check_call(['sudo','date','-s',str])
    except subprocess.CalledProcessError:
        error_out("date execution failed: {0}".format(e))
    #    subprocess.run(['sudo','hwclock','-w'])
    print('done')

set_time(get_gps_datetime())

# put in a cron job, wait 5 min after boot