Sets the SPI clock divider relative to the system clock. On AVR based boards, the dividers available are 2, 4, 8, 16, 32, 64 or 128. The default setting is SPI_CLOCK_DIV4, which sets the SPI clock to one-quarter the frequency of the system clock (4 Mhz for the boards at 16 MHz).
On the Due, the system clock can be divided by values from 1 to 255. The default value is 21, which sets the clock to 4 MHz like other Arduino boards.
Extended method for Arduino Due
If you specify one of the Arduino Due's Slave Select (SS) pin in the call to setClockDivider(), the clock setting is applied only to the device connected to the specified SS pin.
SPI.setClockDivider(divider) SPI.setClockDivider(slaveSelectPin, divider)(Arduino Due only)
- SPI_CLOCK_DIV2 (On AVR boards)
- slave device SS pin (Arduino Due only)
- a number from 1 to 255 (Arduino Due only)