SparkFun 16 Output I/O Expander Breakout - SX1509 (Q742958)

The SX1509 Breakout is a 16-channel GPIO expander with an I2C interface – that means with just two wires, your microcontroller can interface with 16 fully configurable digital input/output pins. But the SX1509 can do so much more than just simple digital pin control. It can produce PWM signals, so you can dim LEDs. It can be set to blink or even breathe pins at varying rates. This breakout is similar to a multiplexer or "mux," in that it allows you to get more IO from less pins.