/*  RTTY carrier modem generator by serial programming the AD9850
  by Alastair GW0AJU
*/
int W_CLK=10; // Pin 10 - connect to AD9850 module word load clock pin (CLK)
int FQ_UD=11; // Pin 11 - connect to freq update pin (FQ)
int DATA=12; // Pin 12 - connect to serial data load pin (DATA)
int RESET=13; // Pin 13 - connect to reset pin (RST).
int RTTY_logic=9; // Pin 9 - TTL output of RTTY data signal logic

// rtty data from left shift, the "b0 = (1 * start low)" + "b1 to b5 = (5 bit data)" + " b6 + b7 = (2 * stop high)" = 8bit single byte

// bit zero is the start bit, next five are the RTTY data, followed by bits 6 and 7 for stop bit. 
// 2 bits are used for the stop instead of the 1.5bits, the extra addition to 2bit for a stop bit will not matter,
// it will only extenduate the data sequence, but still be synchronised by the rtty decoder.


byte info[] = {0x13,0x7F,0x2B,0x57,0x2B,0x57,0x0B,0x23};   // space,letter shift,R,Y,R,Y,carrige return,line feed
unsigned long freq;

void pulseRESET()
{
digitalWrite(RESET, LOW);
delayMicroseconds(50);
digitalWrite(RESET, HIGH);
delayMicroseconds(50);
digitalWrite(RESET, LOW);
}
void pulseW_CLK()
{
digitalWrite(W_CLK, LOW); 
delayMicroseconds(50);
digitalWrite(W_CLK, HIGH);
delayMicroseconds(50);
digitalWrite(W_CLK, LOW);
}
void pulseFQ_UD()
{
digitalWrite(FQ_UD, LOW);
delayMicroseconds(50);
digitalWrite(FQ_UD, HIGH);
delayMicroseconds(50);
digitalWrite(FQ_UD, LOW);
}

// frequency calc from AD9850 datsheet
// program data = (sys clock) * (frequency tuning word)/2^32
void sendFrequency(float frequency)
{
 {   
      freq = frequency * 4294967295/125000000; // note 125 MHz clock on AD9850
      //Serial.println(freq,HEX);
      //Serial.println(freq,DEC);
      for (int b=0; b<4; b++, freq>>=8) 
    {
      tfr_byte(freq & 0xFF); 
    }
   phase();   
 }
}
// transfer the phase info plus trigger AD9850 internal loading
void phase()
  {
      tfr_byte(0x00); // Final control byte, $00 for AD9850 chip
      pulseFQ_UD();// Done! Should see output
  }
// transfers a byte, a bit at a time, LSB first to the 
// AD9850 via serial DATA line
void tfr_byte(byte data)
{
      //Serial.println(data,HEX);
  for (int i=0; i<8; i++, data>>=1) 
        {
          digitalWrite(DATA, data & 0x01);
          pulseW_CLK(); //after each bit sent, CLK is pulsed high
        }
}


void collect_tx_message()   // collect rtty data stream message
{
 byte d;  
  digitalWrite(RTTY_logic, HIGH);  // TTL RTTY output at pin 12
  sendFrequency(14.061445e6); // mark freq = (space freq + 170Hz)    
  for (d=0 ; d<8 ; d++ )  //  d = the number RTTY message + control characters in bytes
      {
       tx_data_message(info[d]);
       //delay(30);
      } 
  digitalWrite(RTTY_logic, HIGH);  // TTL RTTY output at pin 12
  sendFrequency(14.061445e6); // mark freq = (space freq + 170Hz)      
}

void  tx_data_message(byte mess)  // decode data stream message and transmit rtty signal
{
  byte p;
  int sense;
   for (p=0; p<8 ; p++, mess<<=1)  // rtty data sent in pattern due to data sequence
            { 
              
              if ((mess & 0x01) == 0x01)  // detect for mark tone
                  {
                    sense = 1;
                 //  Serial.print("1");
                    digitalWrite(RTTY_logic, HIGH);  // TTL RTTY output at pin 12
                    sendFrequency(14.061445e6); // mark freq = (space freq + 170Hz)
                    delay(20);   // delay period of data bit transmission
                  }
                else if ((mess & 0x01) == 0x00)  // detect for space tone
                  {  
                    sense =0;
                 // Serial.print("0");
                    digitalWrite(RTTY_logic, LOW);   // TTL RTTY output at pin 12
                    sendFrequency(14.061275e6); // space freq
                    delay(20);   // delay period of data bit transmission
                 } 
                 
            }     
  // delay period before retransmission of RTTY message
  // TX tone is mark tone as last used for stop bit of 1.5bits
}
void setup()
{
 // Serial.begin(9600);
// configure arduino data pins for output
pinMode(FQ_UD, OUTPUT);
pinMode(W_CLK, OUTPUT);
pinMode(DATA, OUTPUT);
pinMode(RESET, OUTPUT);
pinMode(RTTY_logic, OUTPUT);
 Serial.begin(9600); 
pulseRESET();
pulseW_CLK();
pulseFQ_UD(); // this pulse enables serial mode
sendFrequency(14.061445e6); // mark freq = (space freq + 170Hz)
}
void loop()
{
  collect_tx_message();
  //delay(500);
//  Serial.println();
}