//  ******************************************** HARDWARE IMPORTANT********************************************************
//  With an Arduino UN0/Nano : uses a potential divider to reduce the voltage:
//
//  MOSI (pin D11) to ADF DATA
//  SCK (pin  D13) to ADF CLK
//  Select (PIN D3) to ADF LE
//
//  Potential divider 560 Ohm with 1000 Ohm to ground on Arduino pins 11, 13 and 3 to adapt from 5V
//  to 3.3V the digital signals DATA, CLK and LE from the Arduino.
//
//  Arduino pin 2 (for lock detection) directly connected to ADF4351 card MUXOUT.
//  ******************************************** HARDWARE IMPORTANT********************************************************
// ***************************************************************************** //
//
// register values for a 1966.5 MHz output
//
// 10MHz clock:  0xC48018,0x8008051,0x4E42,0x4B3,0x95003C,0x58005
//
// 25MHz clock: 0x4E8040,0x80080C9,0x4E42,0x4B3,0x9C803C,0x58005
//
// Copy these values into the array declaration on the line below 
//
// for 1968 MHz use:
//
// 10MHz clock:  0xC48018,0x8008029,0x4E42,0x4B3,0x95003C,0x580005
//
// 25MHz clock:  0x4E8058,0x80080C9,0x4E42,0x4B3,0x9C803C,0x580005
//
// 100MHz
//
// 10 Mhz clock: 0xA00000, 0x8008011, 0x4E42, 0x4B3, 0xD5003C, 0x580005
//
// 500MHz:
//
// 10 Mhz clock: 0xC80000, 0x8008011, 0x4E42, 0x4B3, 0xB5003C, 0x580005
//
// 1000MHz:
//
// 10 Mhz clock: 0xC80000, 0x8008321, 0x4E42, 0x4B3, 0xA503FC, 0x580005
//
// ****************************************************************************** //
#include <SPI.h>
#define ADF4351_CS 7

SPISettings MySettings (10000000, MSBFIRST, SPI_MODE0);

uint32_t registers[6] = {0xA00000, 0x8008011, 0x18004E42, 0x4B3, 0xD502FC, 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);
  delayMicroseconds(200);
  digitalWrite(ADF4351_CS, LOW);
}

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

void setup() 
{

  pinMode(ADF4351_CS, OUTPUT);          // Setup pins
  digitalWrite(ADF4351_CS, HIGH);
  pinMode(LED_BUILTIN, OUTPUT);         // using as a power light!
  digitalWrite(LED_BUILTIN, HIGH);
  SPI.begin();                          // Init SPI bus
    
}

void loop() 
{
  delay (2000);

  SetADF4351();
}