transfer()

SPI transfer is based on a simultaneous send and recieve: the received data is returned in receivedVal. In case of buffer transfer the received data is stored in the buffer in-place (the old data is replaced with the data received) receivedVal = SPI.transfer(val)
val: the byte to send out over the bus.
the received data receivedVal16 = SPI.transfer16(val16)
SPI.transfer(buffer, size)
val16: the two bytes variable to send out over the bus.
the received data (two bytes)
SPI.transfer(buffer, size) buffer: the array of data to be transferred. size: size of the data to be transferred. None