Added script to turn off the system with a button

gpio/turn_off_button/README.md

@@ -0,0 +1,37 @@
+# Turn off the PI using a push button
+
+Simply run the script and hold the push button attached to the correct GPIO port for 5 seconds, this will invoke a subprocess call which will turn off the system.
+
+The script canbe added as a service with the following conf file:
+
+```
+#! /bin/sh
+
+### BEGIN INIT INFO
+# Provides:          turnOffButton.py
+# Required-Start:    $remote_fs $syslog
+# Required-Stop:     $remote_fs $syslog
+# Default-Start:     2 3 4 5
+# Default-Stop:      0 1 6
+### END INIT INFO
+
+# If you want a command to always run, put it here
+
+# Carry out specific functions when asked to by the system
+case "$1" in
+  start)
+    echo "Starting turnOffButton. Listening for 5s pulse..."
+    /usr/local/bin/turnOffButton.py &
+    ;;
+  stop)
+    echo "Stopping turnOffButton."
+    pkill -f /usr/local/bin/turnOffButton.py
+    ;;
+  *)
+    echo "Usage: /etc/init.d/turnOffButton.sh {start|stop}"
+    exit 1
+    ;;
+esac
+
+exit 0
+```

gpio/turn_off_button/turnOffButton.py

@@ -0,0 +1,28 @@
+#!/usr/bin/env python
+import RPi.GPIO as GPIO
+import time
+import subprocess
+
+gpioPin = 3
+definedTime = 5
+
+GPIO.setmode(GPIO.BCM)
+GPIO.setup(gpioPin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
+
+while True:
+    time.sleep(0.2)
+
+    if GPIO.input(gpioPin) == False:
+        print "Button pressed"
+        pressedTime = time.time()
+
+        while GPIO.input(gpioPin) == False:
+            time.sleep(0.2)
+
+        pressedTime = time.time()-pressedTime
+
+        if pressedTime < definedTime:
+            print("Button pressed less than 5 seconds. Time: "+str(pressedTime))
+        else:
+            #print("Button pressed more than 5 seconds. Time: "+str(pressedTime))
+            subprocess.call(['init','0'], shell=False)