examples: Updated python gpio isr example

Example now takes pin number from command line and displays gpio level
when it changes.

Signed-off-by: Henry Bruce <henry.bruce@intel.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

examples/python/hello_isr.py

@@ -24,6 +24,7 @@
 
 import mraa
 import time
+import sys
 
 class Counter:
   count = 0
@@ -32,12 +33,19 @@ c = Counter()
 
 # inside a python interupt you cannot use 'basic' types so you'll need to use
 # objects
-def test(args):
-  print("wooo")
+def test(gpio):
+  print("pin " + repr(gpio.getPin(True)) + " = " + repr(gpio.read()))
   c.count+=1
 
-x = mraa.Gpio(6)
+pin = 6;
+if (len(sys.argv) == 2):
+  try:
+    pin = int(sys.argv[1], 10)
+  except ValueError:
+    printf("Invalid pin " + sys.argv[1])
+print("Starting ISR for pin " + repr(pin))
+x = mraa.Gpio(pin)
 x.dir(mraa.DIR_IN)
-x.isr(mraa.EDGE_BOTH, test, test)
-
-time.sleep(500)
+x.isr(mraa.EDGE_BOTH, test, x)
+var = raw_input("Press ENTER to stop")
+x.isrExit()