This module is an i2c / SPI character LCD backpack with compact design that doesn't cause the mounting obstruction that ordinary boards do. Its basic function is to reduce the number of pins needed to connect to an LCD. It utilizes a general purpose I/O expansion chip, the MCP23008 which has 8 i/o pins (7 are connected) with optional pull-ups, along with a shift register 74HC595 that is used for SPI that has 7 connected outputs.