Transfers one byte over the SPI bus, both sending and receiving. If you specify one of the Slave Select (SS) pin in the call to SPI.transfer(), the specified pin is activated (pulled low) before the transfer occurs and deactivated (pulled high) when the transfer is finished. SPI_LAST parameter is the default. SPI_CONTINUE is not supported in Energia. The last byte to be transferred should be accompanied by the SPI_LAST parameter. By default, if you don’t specify a third parameter, SPI_LAST is used. When a transfer is complete with SPI_LAST, the slave select pin returns inactive (high).


SPI.transfer(slaveSelectPin, val)
SPI.transfer(slaveSelectPin, val, transferMode)


  • val: the value to transfer

  • slaveSelectPin: slave device SS pin

  • transferMode:

    • SPI_LAST: default if not specified the SS pin returns to high after one byte has been transferred.

    • SPI_CONTINUE: the SS pin stays low until transfer is called without transferMode or with SPI_LAST


The byte read from the bus.

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