The Serial Peripheral Interface (SPI) bus is a serial master-slave interface similar to I 2C and comes built in on many microcontrollers. It uses four wires (compared to two on I2C): Serial CLocK (SCLK), Chip Select (CS),Master Out Slave In (MOSI), and Master In Slave Out (MISO). MOSI is used for shifting data into the slave device, and MISO is used for shifting data out of the slave device. Because the SPI bus has dedicated wires for transmitting and receiving data, it can operate in full-duplex mode, unlike the I 2C bus. The typical speed of
operation of SPI is in the low-megahertz range, unlike the mid-kilohertz range on I2C, so the former yields higher throughput.
