This Adafruit MCP23017 I2C GPIO Expander Breakout has 16 GPIO with matching ground pad.
We particularly like the '17 as an expander for it's simple no-nonsense capability. It runs happily from 3V or 5V logic and power. Each GPIO can be an output driving up to 25mA, so LEDs are no problem. Or, each can be an input, with optional pullup. There are two IRQ pins that are configurable for what inputs to keep track of so no I2C bus polling is required. With 3 address pins, you can have up to 8 on a single bus for a total of 8 x 16 = 128 GPIO all on one I2C bus!
Adafruit have got solid and with examples, all ready for this chip. But even if you are using some other platform, the MCP23017 is so classic, you'll likely be able to find example code.
Comes with two sticks of header so you can use it in a breadboard, with some soldering. You can also free-wire buttons by connecting one side to the GPIO (set as input with pullup) and the other side to a ground pad.
To get you going fast, Adafruit spun up a custom-made PCB in the form factor, making it easy to interface with. The on either side are compatible with the I2C connectors. This allows you to make solderless connections between your development board and the MCP23017 or to chain it with a wide range of other sensors and accessories using a compatible cable.
Technical Details
Product Dimensions: 43.0mm x 18.0mm x 5.0mm / 1.7" x 0.7" x 0.2"
