ESP8266 Microchip MCP23S17 Driver
Supports the Microchip MCP23S17 SPI I/O expanders.
Enables the use of up to 128 additional GPIO pins through the SPI bus.
Supports up to 8x MCP23S17 (16 GPIO) chips on the one SPI bus for a total of up to 128 GPIO pins.
Mixing MCP23S08 and MCP23S17 chips on one bus is not currently supported.
Requires my SPI driver: https://github.com/MetalPhreak/ESP8266_SPI_Driver