Added rev auto-check

Author: K. Townsend

Diff for: Adafruit_I2C/Adafruit_I2C.py

@@ -8,7 +8,19 @@
 
 class Adafruit_I2C :
 
-  def __init__(self, address, bus=smbus.SMBus(0), debug=False):
+  def getPiRevision():
+    "Gets the version number of the Raspberry Pi board"
+    # Courtesy quick2wire-python-api
+    # https://github.com/quick2wire/quick2wire-python-api
+    try:
+      with open('/proc/cpuinfo','r') as f:
+        for line in f:
+          if line.startswith('Revision'):
+            return 1 if line.rstrip()[-1] in ['1','2'] else 2
+    except:
+      return 0
+ 
+  def __init__(self, address, bus=smbus.SMBus(1 if getPiRevision() > 1 else 0), debug=False):
     self.address = address
     self.bus = bus
     self.debug = debug