SPI.begin()
SPI.begin(slaveSelectPin)
Initializes the SPI bus by setting SCK, MOSI, and SS to outputs, pulling SCK and MOSI low, and SS high. The default slave select (SS) pin is 2 in Energia but can be changed by passing a parameter for the new slave select.
SPI.begin()
SPI.begin(slaveSelectPin)
slaveSelectPin
: slave device SS pin