Added scripts to Synchronise RPi local time to GPS data

gps_time/LICENSE

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+BSD 3-Clause License
+
+Copyright (c) 2021, LHardwick-git
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+3. Neither the name of the copyright holder nor the names of its
+   contributors may be used to endorse or promote products derived from
+   this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

gps_time/README.md

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+# gps-time
+
+Copyright (c) 2021 LHardwick-git
+Licensed under the BSD 3-Clause license. 
+See LICENSE file in the project root for full license information.
+
+USE CASE
+When running Venus OS on a Raspberry Pi there is no real time clock.
+As my application is on a boat there may be no internet connection.
+In this case the local device time is not set at startup so logs are created with the wrong time stamps.
+
+SOLUTION
+
+This is a shell script that runs at startup and reads the time from the data stream from a USB GPS device. If time information is found in the data stream it is read and used to set the device local time. As a result Venus OS logs are stamped with the correct time.
+
+If the USB GPS device is not connected or not producing a data stream with the right data
+the script will exit. The script is run in the background to ensure that it does not block other
+parts of the Venus OS initialisation.
+
+REQUIREMENTS / TEST ENVIRONMENT
+This has been tested in the following environment.
+It should work in other cases.
+
+   Venus OS 2.6
+   RPI 3B+
+   USB GPS device with NMEA data stream output.
+
+INSTALLATION
+
+Place the gps-time.sh file in directory /data/venus-rpi-setup/
+Make sure it has execute set
+>chmod a+x /data/venus-rpi-setup/gps-time.sh
+
+Place a copy of rc.local in directory /data
+[ Or add the lines from from rc.local to you own rc.local if you need to
+  run other things as well ]
+Make sure rc.local has execute access
+>chmod a+x /data/rc.local
+
+If you choose to out gps-time.sh somewhere else, 
+then change rc.local to refer to the right place.
+
+IN USE
+You can check the results of the script running in the log file.
+/var/volatile/log/gps-time
+
+If all goes well the time on the Venus OS console will be correct at start up.
+
+Hope it works for you 
+
+

gps_time/Scripts/gps-time.sh

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+#!/bin/bash
+# Copyright (c) 2021 LHardwick-git
+# Licensed under the BSD 3-Clause license. 
+# See LICENSE file in the project root for full license information.
+# Read GPS NMEA data from GPS device and use it to set the device (RPi) local time.
+#
+N=0;
+FILE=/run/serial-starter/gps/ttyACM0
+echo "Waiting for GPS data"
+while [ ! -e $FILE ] && [ $N -lt 50 ];
+do
+    sleep 1;
+    ((N++))
+    echo -n "."
+done;
+sleep 5;
+
+if [ $N -ge 49 ]; then
+   echo " GPS data not available is the device plugged in"
+   exit 0;
+fi
+
+echo
+echo "Device attached waiting for data"
+
+input=$FILE
+N=0
+
+# check if GPS has FIX
+LINE1='^\$..GGA,[0-9\.]+,[0-9\.]+,[NS],[0-9\.]+,[EW],([0-2])'
+# Catch lines with date and time info
+LINE2='^\$GPRMC'
+
+FIX=""
+
+# extract date and time from GPS packet
+
+function extract {
+[[ $1 =~ ^\$GPRMC,([0-9]{4})([0-9]{2})\.[0-9]{2},.,[0-9\.]+,[NS],[0-9\.]+,[EW],[0-9\.]*,[0-9\.]*,([0-9]{2})([0-9]{2})([0-9]{2}), ]]
+  COMMAND="20${BASH_REMATCH[5]}${BASH_REMATCH[4]}${BASH_REMATCH[3]}${BASH_REMATCH[1]}.${BASH_REMATCH[2]}"
+  echo command is $COMMAND  
+  date -s $COMMAND
+exit 0
+}
+
+while IFS= read -r line && [ $N -lt 2000 ] 
+do
+#  echo "$line"
+  [[ $line =~ $LINE1 ]] && FIX=${BASH_REMATCH[1]} && echo "GPS device has a fix after $N lines"
+  [[ $line =~ $LINE2 ]] && [[ $FIX -eq 1 ]] && extract $line
+  ((N++))
+done < "$input"
+echo "Timed out no date/time information in 2000 lines from GPS receiver" 

gps_time/Scripts/rc.local

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+# Add these lines to rc.local to run gps-time at startup
+# If you have nothing else to run - this is a perfectly good rc.local file
+
+if test -f /data/venus-rpi-setup/gps.sh; then
+ /data/venus-rpi-setup/gps-time.sh &>>/var/volatile/log/gps-time &
+fi
+exit 0