Power Pins:

  • 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

I2C Logic pins:

  • 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.

Other Pins

  • 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!)

This guide was first published on Feb 10, 2021. It was last updated on May 24, 2024.

This page (Pinouts) was last updated on Mar 08, 2024.

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