----
**IP Selctor**
with the MCP23008 and MCP23017
----

**Preparing the RPi for I2C:**\\
[[http://raspberrypi-aa.github.io/session3/i2c.html]]\\
[[http://www.gsurf.de/vorbereiten-des-raspberry-pi-auf-i2c/]]\\
Open the file:\\
  $ sudo nano /etc/modprobe.d/raspi-blacklist.conf
Comment out:\\
  #blacklist i2c-bcm2708
Open the file:\\
  $ sudo nano /etc/modules
Add:\\
  i2c-dev
Load modules:\\
  $ sudo modprobe i2c_bcm2708
  $ sudo modprobe i2c-dev
Check the i2c modules:\\
  $ lsmod
  
  Module                  Size  Used by
  i2c_dev                 3792  0 
  i2c_bcm2708             3408  0 
Install some programs:\\
  $ sudo apt-get update
  $ sudo apt-get install i2c-tools
  $ sudo apt-get install python-smbus
Check the address:\\
  $ sudo i2cdetect -y 1
  $ sudo i2cdump -y 1 0x20

**Library:**\\
[[https://learn.adafruit.com/mcp230xx-gpio-expander-on-the-raspberry-pi/overview]]\\
Download Adafruit libraries:\\
  $ wget https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code/archive/master.zip
unpack:\\
  $ unzip master.zip
Example:\\
  # Set IP Address with MCP23008
  from Adafruit_MCP230xx import *
  # Use busnum = 0 for older Raspberry Pi's (256MB)
  # Use busnum = 1 for new Raspberry Pi's (512MB with mounting holes)
  mcp = Adafruit_MCP230XX(busnum = 1, address = 0x20, num_gpios = 8)
  # Set pins to input with the pullup resistor enabled
  for i in range(0,8):
    mcp.pullup(i, 1)
  # Read pins and display the results
  # bitshift output, third bit is the output
  meineIP=0
  for i in range(0,8):
    print "%d: %x" % (i, mcp.input(i) >> i)
    meineIP = meineIP +  mcp.input(i)
  print meineIP