#include <SPI.h>

//WA3TFS six meter FM SDR control software REV 39 (TFS-6FM-SDR-R1-0.ino
//JULY 29, 2018  This software may be used for any non-commercial application for amateur radio communications
//Specifically written to support the Super Simple WA3TFS 6 meter FM SDR design
//Sub-audible tone generation madded May 18, 2018

uint32_t frequency;                          //The desired frequency must be divided by 50 ex.51.24Mhz = 1024800
uint32_t tword = frequency * 3435973836 / 125000000;      //tuning word calculation
byte W[5] = {0, 0, 0, 0, 0};
const unsigned char PS_128 = (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);  //these are the prescalers for the ADC sampling rate.
const unsigned char PS_32 = (1 << ADPS2) | (1 << ADPS0);
const unsigned char PS_16 = (1 << ADPS2);
int mic = 512;
unsigned long freq;
unsigned long tempfreq;
unsigned int subtone = 72;                   //SET THE SUBAUDIBLE TONE FREQUENCY IN HERTZ HERE, May not set exactly but within 1/2 Hertz
void setup()

{
  tone(3, 72);                          //IF YOU DO NOT WANT A SUBAUDIBLE TONE, COMMENT OUT THIS COMMAND
  DDRB = B00111110;                          //portb outputs set,
  PORTB = 0x00;

  pinMode (A0, INPUT);                       // here comes the audio frequency in from mic
  SPI.setDataMode(SPI_MODE0);                // set SPI mode 0
  SPI.setClockDivider(SPI_CLOCK_DIV2);       // set SPI speed
  SPI.setBitOrder(LSBFIRST);                 // AD9850 load LSB first
  SPI.begin();
  // set up the ADC
  ADCSRA &= ~PS_128;                         // remove bits set by Arduino library
  ADCSRA |= PS_32;                           // setting the sampling rate at 16MHz/32 this makes the analogRead() complete in around 40μs
  Serial.begin(9600);                        // setup communications with USB port
}

void loop()
{
  if (Serial.available()) {
    freq = Serial.parseInt();
  }

  {
    if (freq >= 50000000 && freq <= 55000000)
    {
      tempfreq = (freq / 50);
      Serial.println("transmit accepted");
      // Serial.println(freq);             //debug
      //  Serial.println(tempfreq);          //debug
    }
    else
    {
      // do nothing, frequency stays last programmed

      {
      }
    }
  }

  {
    if (tempfreq != 0)
    {
      frequency = (tempfreq);
      //Serial.println (frequency);
      
      mic = analogRead(A0);                   //reading the AF from microphone input signal
      frequency = frequency
                  + (2.5 * mic) - 450;        //1024800  this is the Frequency Modulation. the -329 calibrates frequency.  Higher number lowers frequency
                                              //EACH NUMBER CHANGES OUTPUT FREQUENCY BY ABOUT 52 HZ. 
      tword = frequency * 1718;                       //calculating the tuning word for AD9850
      W[0] = (byte) tword;
      W[1] = (byte) (tword >> 8);
      W[2] = (byte) (tword >> 16);           //converting it to bytes
      W[3] = (byte) (tword >> 24);
      W[4] = 0; //phase zero
      //start sending with spi interface
      PORTB = B00000010;                     //call out pin 13,

      PORTB = 0x00;                         //pulse FU_UD
      for (int j = 0; j < 5; j++)
      {
        SPI.transfer(W[j]);                 //send the word to DDS
      }
      PORTB = B00000100;
      PORTB = 0x00;                         //pulse FU_UD
    }
  }
}