title: Input/output error using Python module SMBus, a Raspberry Pi and an Arduino
body: <p>I have connected a <a href="http://en.wikipedia.org/wiki/Raspberry_Pi">Raspberry Pi</a> and <a href="http://en.wikipedia.org/wiki/List_of_Arduino_boards_and_compatible_systems#Software-compatibility_only">Rainbowduino</a> together with a homemade <a href="http://en.wikipedia.org/wiki/I%C2%B2C">I²C</a> level shifter, and installed the <a href="http://en.wikipedia.org/wiki/Python_%28programming_language%29">Python</a> module <a href="http://www.acmesystems.it/i2c">SMBus</a>, the Raspberry Pi can communicate with the Rainbowduino, but every so often I get an input/output error message when trying the command <code>bus.write_i2c_block_data(address, signal, data)</code>.</p>
  
  <p>It says:</p>
  
  <blockquote>
    <p>IOError: [Errno 5] Input/output error</p>
  </blockquote>
  
  <p>Why does it happen and how do I fix or ignore these errors?</p>