What is MOSI in Pi?

Question

What is the significance of these pins MOSI MISO and SS? I am looking at SparkFun DeadOn RTC Breakout - DS3234

Answer 1

They are the SPI (Serial Peripheral Interface) interface pins. SPI is an interface bus used to exchange data between microntrollers and peripherals. It uses four pins MOSI which stands for master out slave in, MISO is Master in slave out, SS is slave select and a clock line (CLK).

You can read more on the SPI protocol on wikipedia and from sparkfun

Answer 2

A MOSI, MISO, CS and CLK are pins of SPI (Serial Peripheral interface protocol)protocol. SPI uses those separate pins to communicate with the target device. The fullform of those pins are serial clock (CLK), Master Input Slave Output (MISO), Master Output Slave Input (MOSI) and Chip Select (CS).

A CLK pin which provides timing information. A MOSI pin which the Pi uses to send information to the device. A MISO pin which the Pi uses to receive information from the device. A Chip select pin which the Pi uses to indicate which device it’s talking to.

This chip select pin is necessary because multiple devices can share the clock, MOSI, and MISO pins, but only one device can be connected to each select pin.