MCP23S08 with ULN2803 SPI I/O extension board expander Arduino Raspberry

This extension board is designed to have 8 output ports over the SPI protocol on a ULN2803 Darlington array. It uses an MCP23S08 SPI controller to drive the ULN2803 Darlington array to switch relays, LEDs, etc. With the DIP switch, You can choose the SPI address, if You need to have two or more board connectors on the same SPI bus.