SPI

setBitOrder()

Sets the order of the bits shifted out of and into the SPI bus, either LSBFIRST (least-significant bit first) or MSBFIRST (most-significant bit first).

// PROTOTYPE
void setBitOrder(uint8_t bitOrder);

// SYNTAX
SPI.setBitOrder(order);

Where, the parameter order can either be LSBFIRST or MSBFIRST.

Note that you must use the same SPI object as used with SPI.begin() so if you used SPI1.begin() also use SPI1.setBitOrder().