MCP23x17 I/O Expanders Microchip Technology MCP23x17 I/O Expanders feature a 16-bit general-purpose parallel bi-directional I/O port with a high-speed I2C interface. These I/O expanders come with three hardware address pins that allow up to eight devices on the bus and configurable interrupt output pins. The hardware pins are used to determine the device address. The MCP23x17 expanders consist of multiple 8-bit configuration registers for input, output, and polarity selection. These MCP23x17 I/O expanders offer two interrupt pins, INTA and INTB, that will activate if either port causes an interrupt.