// include the SPI library:
#include <SPI.h>

const int slaveSelectPin = 10;

 void setup() {
  // set the slaveSelectPin as an output:
  pinMode (slaveSelectPin, OUTPUT);
  // Initializaree SPI:
  SPI.begin();
  SPI.setBitOrder(MSBFIRST); // MSBFIRST 0x00
  SPI.setDataMode(SPI_MODE0); // SPI_MODE0 0x00
  SPI.setClockDivider(SPI_CLOCK_DIV4); // SPI_CLOCK_DIV4 0x00
}

 void SPIClass::begin() {
  // Set SS to high so a connected chip will be "deselected" by default
  digitalWrite(SS, HIGH);
  // When the SS pin is set as OUTPUT, it can be used as
  // a general purpose output port (it doesn't influence
  // SPI operations).
  pinMode(SS, OUTPUT);
  // Warning: if the SS pin ever becomes a LOW INPUT then SPI
  // automatically switches to Slave, so the data direction of
  // the SS pin MUST be kept as OUTPUT.
  SPCR |= (1<<MSTR); // Set as master
  SPCR |= (1<<SPE); // SPI enable
  // Set direction register for SCK and MOSI pin.
  // MISO pin automatically overrides to INPUT.
  // By doing this AFTER enabling SPI, we avoid accidentally
  // clocking in a single bit since the lines go directly
  // from "input" to SPI control.  
  pinMode(SCK, OUTPUT);
  pinMode(MOSI, OUTPUT);
}