Easily access the powerful MCP23017 I2C 16-bit Port Expander with this breakout board from PMD Way. It contains the useful port expander on a hardy PCB breakout board.

The MCP23017 allows you to add sixteen inputs or outputs (in two pairs of eight) easily to any platform with an I2C interface. The MCP23017 is easy to use, and quite hardy.   

Furthermore, this breakout board is designed to be used with 16x2 and 20x4 character LCDs along with the classic 128x64 graphic LCD - allowing you to control the display with only the I2C instead of a bunch of digital output pins.

There is also a contrast potentiometer and the option of PWM control for backlight brightness. Inline header pins are included but not soldered to the board.

Features

    16-bit input/output port expander with interrupt output
    Cascadable for up to 8 devices on one bus
    25mA sink/source capability per I/O
    Supports 100kHz, 400kHz and 1.7MHz I2C™Compatible compatible modes

More information

    Arduino LCD and MCP23017 library
    Excellent MCP23017 and Arduino tutorial
    Arduino library for those in a hurry   

    Arduino learn
    download MCP23017 data sheet (.pdf)
    Raspberry Pi tutorial