#include <SPI.h> 

const int slaveSelectPin = 13 ;
byte data = 0x55 ;

// set up the speed, mode and endianness of each device
SPISettings settingsA(2000000, MSBFIRST, SPI_MODE1); 

void setup() 
{
  // set the slaveSelectPin as an output:
  pinMode (slaveSelectPin, OUTPUT);
  // initialize SPI:
  SPI.begin(); 
}

void loop() 
{
  // data += 1 ;
  SPI.transfer(data) ;
}