#include <SPI.h>
#define ADF4351_CS 3
#define LOCK 2

uint32_t registers[6] = {0x500000, 0x8008011, 0x4E42, 0x4B3, 0xAC82FC, 0x580005};

void WriteReg32(const uint32_t value)
{
  digitalWrite(ADF4351_CS, LOW);
  for (int i = 3; i >= 0; i--)             // loop round 4 x 8 bits
    SPI.transfer((value >> 8 * i) & 0xFF); // offset, byte mask and send via SPI
  digitalWrite(ADF4351_CS, HIGH);
  digitalWrite(ADF4351_CS, LOW);
}

void SetADF4351()  // bung the data into the ADF4351
{ for (int i = 5; i >= 0; i--)
    WriteReg32(registers[i]);
}

void setup() 
{
  pinMode(LOCK,INPUT);
  pinMode(ADF4351_CS, OUTPUT);          // Setup pins
  digitalWrite(ADF4351_CS, HIGH);
  SPI.begin();                          // Init SPI bus
  SPI.setDataMode(SPI_MODE0);
  SPI.setBitOrder(MSBFIRST);
}

void loop() 
{
  delay (5000);

  SetADF4351();
}