Transfers one byte over the SPI bus, both sending and receiving.
// SYNTAX SPI.transfer(val); SPI1.transfer(val);
Where the parameter
val, can is the byte to send out over the SPI bus.
Note that you must use the same
SPI object as used with
SPI.begin() so if you used
SPI1.begin() also use
transfer() acquires the SPI peripheral lock before sending a byte, blocking other threads from using the selected SPI peripheral during the transmission. If you call
transfer in a loop, call
beginTransaction() function before the loop and
endTransaction() after the loop, to avoid having another thread interrupt your SPI operations.