This product has been retired. It has been replaced by the Grove I2C GPIO Extender located here: https://store.switchdoc.com/grove-digital-extender-i2c-board/
I2C 8 GPIO Extender (Dual Pack - you get two individual boards) - Adds 8 GPIO pins to your device through an inexpensive I2C Breakout Board. This board is an inexpensive I2C GPIO Extender Board. It allows you to add 8 pins of GPIO, with interrupts allowed on all pins, to any Arduino or Raspberry Pi design. It works with 5V and 3.3V and in fact you can have 4 pins at 5.0V while having 4 pins at 3.3V at the same time. It is based upon the Semtech SX1502 and it has some really cool features. What are some of the applications for this 8 GPIO Extender board? Anytime you need additional GPIO pins. This happens all the time with the Raspberry Pi and with some of the newer, smaller Arduino boards. Do you want more interrupts on your Arduino or Raspberry Pi? You can use this board to generate interrupts that can then be read by the Arduino or Raspberry Pi. The other advantage is that you can set each bank of four GPIOs to a different power supply, anywhere from 1.2V to 5.5V. Very flexible in mixed voltage systems. Of course, the board is both 3.3V and 5.0V tolerant meaning your I2C bus can be at either of those voltages. Another more subtle advantage of this board is that you can create logic gates (PLD - Programmable Logic Device). Do you need a couple of logic gates in your design? You can build XOR, Inverters, AND, NAND, OR, NOR, etc., etc. using this chip. Your choice!