On Ubuntu, a common scheduling utility, cron daemon can be used with a script
to monitor the AC and battery status and control system shutdown by controlling three signals of UPS3.

Auto shutdown Script

This script checks the status of power and battery.
Save the following code as ups3.sh in home directory.
Note that this script can be used with U3 as well as C1/C1+/C2 without modification.

Let's assume that ups3.sh is located in /home/odroid/ups3.sh.

#!/bin/sh
MODEL=$(cat /proc/cpuinfo | grep ^Hardware | awk -F " " '{print $3}')
SYSFS_GPIO_DIR="/sys/class/gpio"
 
retval=""
 
gpio_export()
{
        [ -e "$SYSFS_GPIO_DIR/gpio$1" ] && return 0
        echo $1 > "$SYSFS_GPIO_DIR/export"
}
 
gpio_getvalue()
{
	echo in > "$SYSFS_GPIO_DIR/gpio$1/direction"
        val=`cat "$SYSFS_GPIO_DIR/gpio$1/value"`
        retval=$val
}
 
gpio_setvalue()
{
	echo out > "$SYSFS_GPIO_DIR/gpio$1/direction"
        echo $2 > "$SYSFS_GPIO_DIR/gpio$1/value"
}
 
if test $MODEL = "ODROIDC"
then
        AC_OK_GPIO=88
        BAT_OK_GPIO=116
	LATCH_GPIO=115
	gpio_export $LATCH_GPIO 
	gpio_setvalue $LATCH_GPIO 1
elif test $MODEL = "ODROID-C2"
then
        AC_OK_GPIO=247
        BAT_OK_GPIO=239
	LATCH_GPIO=225
	gpio_export $LATCH_GPIO 
	gpio_setvalue $LATCH_GPIO 1
else 
        AC_OK_GPIO=199
        BAT_OK_GPIO=200
fi
 
gpio_export $AC_OK_GPIO
gpio_export $BAT_OK_GPIO
gpio_getvalue $AC_OK_GPIO
if [ $retval -eq  1 ]
then
        echo "DC Input Okay"
else
        echo "Power is shutdown or AC Adapter is disconnected"
        gpio_getvalue $BAT_OK_GPIO
        echo $retval
        if [ $retval -eq 0 ]
        then
                echo "battery is lower than 3.7V"
                /sbin/shutdown -P 1
        else
                echo "battery is good"
        fi
fi

Give execute permission to everybody with following command.

target

$ sudo chmod a+x /home/odroid/ups3.sh

Cron setup

This can be set up by running crontab.

target

$ sudo crontab -e

This example script will run ups3.sh script every 2 minutes.

target

# m h  dom mon dow   command
*/2 * * * * /home/odroid/ups3.sh

To confirm that cron works with ups3.sh, check the syslog.

target

$ tail -f /var/log/syslog
...
...
Jul 25 04:53:01 odroid64 CRON[1824]: (root) CMD (/home/odroid/ups3.sh)
Jul 25 04:53:01 odroid64 CRON[1823]: (CRON) info (No MTA installed, discarding output)
...
Jul 25 04:55:01 odroid64 CRON[1960]: (root) CMD (/home/odroid/ups3.sh)
Jul 25 04:55:01 odroid64 CRON[1959]: (CRON) info (No MTA installed, discarding output)
...

On Android, you need to register the monitoring script, ups3.sh in android init rc.

Auto shutdown Script

Here is an example script for Android and the default path is /system/bin/ups3.sh.

#!/bin/sh
SYSFS_GPIO_DIR="/sys/class/gpio"
 
retval=""
 
gpio_export()
{
	[ -e "$SYSFS_GPIO_DIR/gpio$1" ] && return 0
	echo $1 > "$SYSFS_GPIO_DIR/export"
	echo $1
}
 
gpio_getvalue()
{
	echo in > "$SYSFS_GPIO_DIR/gpio$1/direction"
	val=`cat "$SYSFS_GPIO_DIR/gpio$1/value"`
	retval=$val
}
 
gpio_setvalue()
{
	echo out > "$SYSFS_GPIO_DIR/gpio$1/direction"
	echo $2 > "$SYSFS_GPIO_DIR/gpio$1/value"
}
 
check()
{
	gpio_export $AC_OK_GPIO
	gpio_export $BAT_OK_GPIO
	gpio_getvalue $AC_OK_GPIO
 
	if [ $retval -eq  1 ]
	then
		echo "DC Input Okay"
		lowVoltageCount=0
	else
		echo "Power is shutdown or AC Adapter is disconnected"
		gpio_getvalue $BAT_OK_GPIO
		echo $retval
		if [ $retval -eq 0 ]
			then
				echo "battery is low than 3.7V"
				sleep 118
				lowVoltageCount=$(( lowVoltageCount+1 ))
				if [ $lowVoltageCount  -gt 5 ]
				then
					echo "power off"
					am start -a android.intent.action.ACTION_REQUEST_SHUTDOWN --ez KEY_CONFIRM true --activity-clear-task
				fi
		else
			echo "battery is good"
		fi
	fi
}
 
MODEL=`getprop ro.product.board`
echo $MODEL
 
if [ `echo $MODEL | grep -c "odroidc2"` -gt 0 ]
then
	AC_OK_GPIO=247
	BAT_OK_GPIO=239
	LATCH_GPIO=225
	gpio_export $LATCH_GPIO
	gpio_setvalue $LATCH_GPIO 1
elif [ `echo $MODEL | grep -c "odroidc"` -gt 0 ]
then
	AC_OK_GPIO=88
	BAT_OK_GPIO=116
	LATCH_GPIO=115
	gpio_export $LATCH_GPIO
	gpio_setvalue $LATCH_GPIO 1
else
	AC_OK_GPIO=199
	BAT_OK_GPIO=200
	LATCH_GPIO=204
	gpio_export $LATCH_GPIO
	gpio_setvalue $LATCH_GPIO 1
fi
 
lowVoltageCount=0
while true
do
	check
	sleep 2
done

Register the monitoring service in Android init

To enable UPS service, add a service routine in the Android init rc.
For each model, the default path is different.

• C1/C1+ : /init.odroid.board.rc
• C2 : /init.odroid2.board.rc

target

shell@odroidc2:/ $ su
root@odroidc2:/ # mount -o rw,remount /
[  298.823337] EXT4-fs (mmcblk0p2): re-mounted. Opts: (null)
root@odroidc2:/ # vi /init.odroidc2.board.rc

service ups /system/bin/ups3.sh
    class core
    user root                                                                
    group root
#    disabled
    oneshot

As aforementioned, ups3.sh and init routine are added by default since a specific Android version.
If you have the new version, only make sure to block disabled part of ups3 service in /init.odroid2.board.rc or /init.odroid.board.rc.