- VIN - This is the power pin. To power the expander breakout board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
- GND - common ground for power and logic
SCL - I2C clock pin, connect to your microcontroller I2C clock line.
- SDA - I2C data pin, connect to your microcontroller I2C data line.
- STEMMA QT - These connectors allow you to connectors to dev boards with STEMMA QT connectors or to other things with various associated accessories
- 0 - 15 - GPIO expander pins for LED drive (current-source dimming) or GPIO mode. Can be used as input or output. Supports 8-bit linear constant-current LED dimming support so you can connect LEDs without resistors. Note that this chip does not support internal pull-up or pull-downs, so you will need to add an external resistor if you need one.
- INT - Interrupt output pin, can alert you when input value changes.
- RST - Hardware reset pin, set low to perform a hardware reset. Has 10kΩ pull-up resistor.
- A0 and A1 jumpers - These can be used to change the default I2C address from 0x58 to 0x59 (A0 shorted), 0x5A (A1 shorted) or 0x5B (both shorted!)