#!/bin/bash

# Check PPS and if GPS NMEA is Acquired

# Files;
# Acquired status count file
ACNTFILE="/var/local/lib/gps-chk/acqrd-cnt"
# Previous acquired status file
ASTATFILE="/var/local/lib/gps-chk/acqrd-stat"
# PPS count file
PCNTFILE="/var/local/lib/gps-chk/pps-cnt"

# Serial port
DEV="/dev/Your_TtySx"

# Current acquired status
CURASTAT=$( /usr/local/sbin/chk-gps-acqrd.sh )
# Previous status
PREVASTAT=$( /bin/cat "${ASTATFILE}" )
# Not acquired status count
ASTATCNT=$( /bin/cat "${ACNTFILE}" )
# Max not acquired count
MAXACNT=2
# Current sync quality
CURSYNC=$( /usr/local/sbin/ntpeval )
# PPS count
PPSCNT=$( /bin/cat "${PCNTFILE}" )
# PPS Reset delay.
RSTDLY=8

# Check PPS;
REACH=$( /usr/bin/ntpq -p | egrep "^[ *+](SHM|127[.]127[.]28[.])" | awk '{print $7}' )
# Force REACH 0 if not spresent
if [ ! $REACH ]
then
	REACH=0
fi
# Convert to decimal
REACH=$(( 8#$REACH ))

# Check PPS reach
if [ $(( $REACH%2 )) -eq 0 ]
then
	# Bits xxxx xxx0; even => Missing
	logger "chk-gps: PPS Failed"
	if [ $PPSCNT -gt 0 ] && [ $(( $PPSCNT%$RSTDLY )) -eq 0 ]
	then
		# Garmin may have crashed: Reset Garmin
		sleep 10
		echo $REACH | mail -s "Garmin PPS Reset" Your_Email_Address
		logger "chk-gps: PPS Reset"
		/usr/local/sbin/sndnul -d "${DEV}" -t 2
		sleep 5
	fi
	let PPSCNT+=1
	echo $PPSCNT > "${PCNTFILE}"
	# Exit script
	exit 0
else
	# Bits xxxx xxx1; odd => OK
	if [ $PPSCNT -ne 0 ]
	then
		# Was missing
		logger "chk-gps: PPS OK"
		echo 0 > "${PCNTFILE}"
	fi
fi

# Check NMEA
if [ $CURASTAT -eq 0 ]
then
	# Not acquired
	let ASTATCNT+=1
	echo $ASTATCNT > "${ACNTFILE}"
	if [ $ASTATCNT -gt $MAXACNT ] && [ $CURSYNC -eq 0 ] && [ $PREVASTAT -ne 0 ]
	then
		# Reset Garmin
		logger "chk-gps: NMEA Failed"
		/usr/local/sbin/sndnul -d "${DEV}" -t 2
		sleep 5
		echo 0 > "${ASTATFILE}"
	fi
else
	# Acquired
	if [ $ASTATCNT -ne 0 ]
	then
		# Was not acquired
		echo 0 > "${ACNTFILE}"
	fi
	if [ $PREVASTAT -ne 1 ]
	then
		logger "chk-gps: NMEA OK"
		echo 1 > "${ASTATFILE}"
	fi
fi