Simple shell script to determine GPIO -> LED mappings on embedded linux devices

gpio_blink.sh

#!/bin/ash

# This script is a helper for creating GPIO -> LED mappings on openwrt devices
# Just run it and watch for blinking LEDs on your device.
# If your device does crash/reboot while running this script you can limit
# which GPIOs it addresses. Just take the number of the last GPIO the script
# displayed before the device rebooted, increment it by one and call the script again:
# ./gpio_blink.sh <number>

min=0
[ -n "$1" ] && echo "$1" | egrep -q '[0-9]+' && min="$1"
for gpio in `seq "$min" 100`; do
	echo "$gpio" > /sys/class/gpio/export 2> /dev/null && \
	echo "Exporting gpio${gpio}"
done

for f in /sys/class/gpio/*; do
	gpio="$(echo "$f" | egrep -o 'gpio[0-9]+$')"
	[ -n "$gpio" ] || continue
	echo "Enabling $gpio"
	echo out > "$f/direction"
	echo "Blinking $gpio"
	state=0
	for i in `seq 3`; do
		if [ $state -eq 0 ];  then
			echo 1 > "$f/value"
			state=1
		else
			echo 0 > "$f/value"
			state=0
		fi
		sleep 1
	done
	echo ======
done