RPI LCD Interrupt

This program runs on Raspberry pi plus the Adafruit RGB 16x2 LCD+Keypad Kit
The purpose of this program is to use the interrupts instead of constantly polling the
Buttons. This is a modifiation of Adafruit_CharLCDPlate.py. We enable the interrupts on
both the MCP23017 AND the Raspberry Pi GPIO. Then we electrically link them:

The MCP23017 INTA pin is connected to Raspberry pi GPIO 23 through a resistor divider,
to reduce the MCP23017 5V to an acceptable level for the pi.

  +----------------------+
  |                      |         +---------+        +-----------+
  |  MCP23017          20|+------->| 680 Ohms|+--+--->| 820 Ohms  |<-------+ GND
  |                      |         +---------+   |    +-----------+
  +----------------------+                       v
                                              GPIO 23

Just make sure you have the latest RPi.GPIO version   https://pypi.python.org/pypi/RPi.GPIO

Then run this software:
$ sudo python UseInterruptGPIO.py

and press the buttons..
Interrupts do it better:-)