Battery protection for the nokia n900 running PostmarketOS

n900-battery-monitor

#!/bin/sh

# Battery protection for the nokia n900
# When battery level falls below 8% gives led notification.
# When battery level falls below 6% powers off the device.
#
# To use it, place the script in `/sbin`, make it executable 
# `sudo chmod +x /sbin/n900-battery-monitor`, then add
# `::respawn:/sbin/n900-battery-monitor` to /etc/inittab, 
# or create a service for it.

# Disable battery charger's status pin
echo 0 > /sys/class/power_supply/bq24150a-0/stat_pin_enable

function alert_low_bat {
	LED="/sys/class/leds/lp5523:r/brightness"
	while true; do
		echo 50 > $LED 
		sleep 0.1

		echo 0 > $LED 
		sleep 0.1

		echo 50 > $LED 
		sleep 0.5

		echo 0 > $LED 
		sleep 0.5
	done
}

ALERT_PID=""

while true; do

	CAPACITY=$(cat /sys/class/power_supply/bq27200-0/capacity)
	STATUS=$(cat /sys/class/power_supply/bq27200-0/status)

	if [ $CAPACITY -le 8 ] && 
	   [ "$STATUS" = "Not charging" ] &&
	   [ "$ALERT_PID" = "" ];
	then
		alert_low_bat &
		ALERT_PID=$!
	
	elif [ $CAPACITY -gt 8 ] ||
	     [ "$STATUS" = "Charging" ] && 
	     [ "$ALERT_PID" != "" ];
	then
		kill $ALERT_PID
		ALERT_PID=""
		LED="/sys/class/leds/lp5523:r/brightness"
		echo 0 > $LED

	elif [ $CAPACITY -le 6 ] &&
	     [ "$STATUS" = "Not charging" ];
	then 
		/sbin/poweroff

	fi

	sleep 60

done