Adafruit PCF8575 I2C 16 GPIO Expander Breakout

Key Features It has 16 I/O pins Three I2C address select jumpers mean up to 8 expanders to one bus for 128 total GPIO added Each pin can be an input with light pull-up or an output sink IRQ output will automatically alert you when input pins change value This chip does not have a pin direction register. You cannot set the pins as input or output - instead, each pin has two possible states. GPIO expanders work like this: you have a board with some number of GPIO but not enough for your project - maybe you need more buttons or LEDs. You could upgrade to a board with massive number of GPIO like the Grand Central, or you could pop on one of these boards. Connect it over I2C and then you can send/receive I2C commands to control the GPIO pins to write and read them. It's going to be slower than direct GPIO access, but maybe that doesn't matter if it takes a millisecond instead of a microsecond. You only need the two I2C pins, and you can even share the I2C port with oth