MCP23008 - I2C 8 Input/Output Port Expander IC - 5 Pack
Add another eight input or output pins to your Arduino or other development board with the MCP23008 I/O port expander IC from PMD Way. You can set each of the eight pins to be input, output, input with a pullup or open drain.
There's even the ability to get an interrupt via an external pin when any of the inputs change so you don't have to keep polling the chip. You can use up to eight MCP23008s on the one I2C bus as there is eight possible bus addresses.
You can sink or source up to 20mA from any of the I/O pins so this will work for LEDs and small relays. Team it up with a high-power MOSFET if you need to control more current.
- Chip Configuration: 8 bit
- Bus Frequency: 1.7MHz
- IC Interface Type: I2C, Serial
- No. of I/O's: 8
- Supply Voltage Range: 1.8V to 5.5V
- Digital IC Case Style: DIP
- No. of Pins: 18
- Delay Time: 50ns
- Download Data sheet (.pdf)
- Adafruit have a nice Arduino library
- Raspberry Pi tutorial