The two on-board mini PCIe card sockets accept a variety of plug-in modules such as Wi-Fi modems, analog to digital converters, GPS receivers, additional Ethernet ports, flash data storage and other small sized plug-in cards for added flexibility. There are two full size sockets that provide PCIe and USB interfaces. One of these sockets also supports an mSATA interface. The SPI/SPX expansion connector allows low-cost analog and digital SPI interconnect expansion modules to be easily added to the system. SPX expansion that uses the SPI protocol provides an easy way to add low-cost, low-speed I/O expansion such as Analog Inputs or Digital I/O.