MCP23008 - i2c 8-bit Input/Output Port Expander - (AD34108)

Description:

Add 8 more pins to your microcontroller with an MCP23008 port expander. The MCP23008 uses two i2c pins (which can be shared with other i2c devices) and in exchange, you get 8 general-purpose pins. You can configure each of the 8 pins as an input, output, or input with a pull-up. You can even get an interrupt through an external pin when any of the inputs change, thereby avoiding constant polling of the chip.

Use this chip from 2.7 to 5.5 V and you can supply/receive up to 20 mA from any of the I/O pins, which will work with LEDs and the like. Combine it with a high-power MOSFET if you need more power. Thanks to its DIP package, it connects to any breadboard or perfboard.

You can configure the I2C address by connecting the ADDR0-2 pins to power or ground, for up to 8 unique addresses. This means that 8 chips can share a single I2C bus: 64 I/O pins!

We use this chip in our SPI/I2C backpack and found it to be very reliable and easy to configure. We even have an Arduino library with example code that sets pin states, reads and writes from individual pins, and configures pullups.

Datasheet

Reference Link 1

Reference Link 2