In the world of communication protocols, SPI is often considered as “Little” communication protocol compared to Ethernet, USB and others. Ethernet and USB are meant for “Outside the box communications” and data exchanges between whole systems. While SPI, as well as I2C are well suited for communications between integrated circuits for low/medium data transfer speed with on-board peripherals. SPI allows a full duplex, synchronous and serial communication between the MCU and peripheral devices. SPI is often referred to as SSI (Synchronous Serial Interface).