The Serial Peripheral Interface Bus or SPI bus is a synchronous serial data link standard named by Motorola that operates in full duplex mode. Devices communicate in a master/slave mode where the master device initiates the data frame. Multiple slave devices are allowed with individual slave select (chip select) lines using a pin for each device. The transfer() method exchanges bytes of data.
SPI.transfer(val) SPI.transfer(slaveSelectPin, val)(Arduino Due only) SPI.transfer(slaveSelectPin, val, transferMode)(Arduino Due only)
- val: the byte to send out over the bus
- slaveSelectPin: slave device SS pin (Arduino Due only)
- transferMode (Optional, Arduino Due only)
- SPI_CONTINUE: keeps the SS pin low, allowing a subsequent byte transfer.
- SPI_LAST: default if not specified the SS pin returns to high after one byte has been transferred.