Generate PSK with an Arduino and Si5351

Si5351_PSK_Ext.ino

#include <si5351.h>
#include "Wire.h"
 
Si5351 si5351;

uint16_t varicode[] =
{
  0b1010101011000000,  // 0 NUL 
  0b1011011011000000,  // 1 SOH
  0b1011101101000000,  // 2 STX
  0b1101110111000000,  // 3 ETX
  0b1011101011000000,  // 4 EOT
  0b1101011111000000,  // 5 ENQ
  0b1011101111000000,  // 6 ACK
  0b1011111101000000,  // 7 BEL
  0b1011111111000000,  // 8 BS
  0b1110111100000000,  // 9 HT
  0b1110100000000000,  // 10 LF
  0b1101101111000000,  // 11 VT
  0b1011011101000000,  // 12 FF
  0b1111100000000000,  // 13 CR
  0b1101110101000000,  // 14 SO
  0b1110101011000000,  // 15 SI
  0b1011110111000000,  // 16 DLE
  0b1011110101000000,  // 17 DC1
  0b1110101101000000,  // 18 DC2
  0b1110101111000000,  // 19 DC3
  0b1101011011000000,  // 20 DC4
  0b1101101011000000,  // 21 NAK
  0b1101101101000000,  // 22 SYN
  0b1101010111000000,  // 23 ETB
  0b1101111011000000,  // 24 CAN
  0b1101111101000000,  // 25 EM
  0b1110110111000000,  // 26 SUB
  0b1101010101000000,  // 27 ESC
  0b1101011101000000,  // 28 FS
  0b1110111011000000,  // 29 GS
  0b1011111011000000,  // 30 RS
  0b1101111111000000,  // 31 US
  0b1000000000000000,  // 32 SP
  0b1111111110000000,  // 33 !
  0b1010111110000000,  // 34 "
  0b1111101010000000,  // 35 #
  0b1110110110000000,  // 36 $
  0b1011010101000000,  // 37 %
  0b1010111011000000,  // 38 &
  0b1011111110000000,  // 39 '
  0b1111101100000000,  // 40 (
  0b1111011100000000,  // 41 )
  0b1011011110000000,  // 42 *
  0b1110111110000000,  // 43 +
  0b1110101000000000,  // 44 ,
  0b1101010000000000,  // 45 -
  0b1010111000000000,  // 46 .
  0b1101011110000000,  // 47 /
  0b1011011100000000,  // 48 0
  0b1011110100000000,  // 49 1
  0b1110110100000000,  // 50 2
  0b1111111100000000,  // 51 3
  0b1011101110000000,  // 52 4
  0b1010110110000000,  // 53 5
  0b1011010110000000,  // 54 6
  0b1101011010000000,  // 55 7
  0b1101010110000000,  // 56 8
  0b1101101110000000,  // 57 9
  0b1111010100000000,  // 58 :
  0b1101111010000000,  // 59 ;
  0b1111011010000000,  // 60 <
  0b1010101000000000,  // 61 =
  0b1110101110000000,  // 62 >
  0b1010101111000000,  // 63 ?
  0b1010111101000000,  // 64 @
  0b1111101000000000,  // 65 A
  0b1110101100000000,  // 66 B
  0b1010110100000000,  // 67 C
  0b1011010100000000,  // 68 D
  0b1110111000000000,  // 69 E
  0b1101101100000000,  // 70 F
  0b1111110100000000,  // 71 G
  0b1010101010000000,  // 72 H
  0b1111111000000000,  // 73 I
  0b1111111010000000,  // 74 J
  0b1011111010000000,  // 75 K
  0b1101011100000000,  // 76 L
  0b1011101100000000,  // 77 M
  0b1101110100000000,  // 78 N
  0b1010101100000000,  // 79 O
  0b1101010100000000,  // 80 P
  0b1110111010000000,  // 81 Q
  0b1010111100000000,  // 82 R
  0b1101111000000000,  // 83 S
  0b1101101000000000,  // 84 T
  0b1010101110000000,  // 85 U
  0b1101101010000000,  // 86 V
  0b1010111010000000,  // 87 W
  0b1011101010000000,  // 88 X
  0b1011110110000000,  // 89 Y
  0b1010101101000000,  // 90 Z
  0b1111101110000000,  // 91 [
  0b1111011110000000,  // 92 backslash
  0b1111110110000000,  // 93 ]
  0b1010111111000000,  // 94 ^
  0b1011011010000000,  // 95 _
  0b1011011111000000,  // 96 `
  0b1011000000000000,  // 97 a
  0b1011111000000000,  // 98 b
  0b1011110000000000,  // 99 c
  0b1011010000000000,  // 100 d
  0b1100000000000000,  // 101 e
  0b1111010000000000,  // 102 f
  0b1011011000000000,  // 103 g
  0b1010110000000000,  // 104 h
  0b1101000000000000,  // 105 i
  0b1111010110000000,  // 106 j
  0b1011111100000000,  // 107 k
  0b1101100000000000,  // 108 l
  0b1110110000000000,  // 109 m
  0b1111000000000000,  // 110 n
  0b1110000000000000,  // 111 o
  0b1111110000000000,  // 112 p
  0b1101111110000000,  // 113 q
  0b1010100000000000,  // 114 r
  0b1011100000000000,  // 115 s
  0b1010000000000000,  // 116 t
  0b1101110000000000,  // 117 u
  0b1111011000000000,  // 118 v
  0b1101011000000000,  // 119 w
  0b1101111100000000,  // 120 x
  0b1011101000000000,  // 121 y
  0b1110101010000000,  // 122 z
  0b1010110111000000,  // 123 {
  0b1101110110000000,  // 124 |
  0b1010110101000000,  // 125 }
  0b1011010111000000,  // 126 ~
  0b1110110101000000   // 127 (del)
};

volatile int index = 0;
volatile uint16_t symbol;
volatile int psk_bit = 0;
volatile int zero_count = 0;
volatile int set_vfo = 0;

const uint16_t baud_rate = 3125;
//const uint16_t baud_rate = 6250;
const uint16_t clock_mult = 1000;
uint32_t freq = 14100000UL;
uint32_t clock_freq = baud_rate * clock_mult;
String mystring = "DE NT7S CN85NM\n";
int psk_bit_prev = 0;
const unsigned long long pll_freq = 87000000000ULL;

int led = 13;
int external_clock_pin = 2;

void setup()
{
  Serial.begin(57600);
  
  // Setup external interrupt for clock input
  pinMode(external_clock_pin, INPUT);
  attachInterrupt(0, ext_clock, RISING);
  
  // Initialize the Si5351A
  si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0);
  
  delay(10);
  
  uint8_t temp = si5351.si5351_read(16);
  Serial.println(temp, HEX);
  temp = si5351.si5351_read(17);
  Serial.println(temp, HEX);

  si5351.set_correction(-67);
  //si5351.si5351_write(187, 0x92);

  si5351.set_pll(pll_freq, SI5351_PLLA);
  //si5351.set_pll(pll_freq, SI5351_PLLB);
  si5351.si5351_write(16, 0x80);
  si5351.si5351_write(17, 0x80);
  //si5351.si5351_write(18, 0x80);
  si5351.set_ms_source(SI5351_CLK0, SI5351_PLLA);
  si5351.set_ms_source(SI5351_CLK1, SI5351_PLLA);
  si5351.set_ms_source(SI5351_CLK2, SI5351_PLLA);
  
  si5351.set_freq((freq * 100ULL), pll_freq, SI5351_CLK0);
  si5351.set_freq((freq * 100ULL), pll_freq, SI5351_CLK1);
  si5351.set_freq((3138100ULL), pll_freq, SI5351_CLK2);
  
  si5351.set_phase(SI5351_CLK0, 0);
  si5351.set_phase(SI5351_CLK1, 0);
  si5351.set_phase(SI5351_CLK2, 0);
  
  
  si5351.si5351_write(16, 0x0c);
  si5351.si5351_write(17, 0x0c);
  si5351.si5351_write(18, 0x0c);
  si5351.pll_reset(SI5351_PLLA); 

  // Load the first varicode symbol from the message
  symbol = varicode[mystring.charAt(index)];
  
  // We'll flash the LED in sync with the PSK modulation
  pinMode(led, OUTPUT);
  
  /*
  // Set up Timer1 for interrupts at 31.25 Hz
  cli(); //stop interrupts
  TCCR1A = 0;// set entire TCCR1A register to 0
  TCNT1  = 0;//initialize counter value to 0
  // set compare match register
  if(baud_rate == 3125)
  {
    OCR1A = 7969d;// = (16*10^6) / (1*1024) - 1 (must be <65536)
    //OCR1A = 499;// = (16*10^6) / (1*1024) - 1 (must be <65536)
  }
  else if(baud_rate == 6250)
  {
    OCR1A = 250;
  }
  // turn on CTC mode, set CS12 and CS10 bits for 1024 prescaler
  //TCCR1B = (1 << WGM12) | (1 << CS12) | (1 << CS10);
  
  // 64
  TCCR1B = (1 << WGM12) | (1 << CS11) | (1 << CS10);
  // enable timer compare interrupt
  TIMSK1 = (1 << OCIE1A);
  sei(); //allow interrupts*/
}

/*
ISR(TIMER1_COMPA_vect)
{
  if(symbol == 0)
  {
    if(zero_count)
    {
      psk_bit = 0;
      zero_count--;
    }
    else
    {
      index++;
    
      // Reset message pointer to beginning of string if at end
      if(index >= mystring.length())
      {
        index = 0;
      }
      
      symbol = varicode[mystring.charAt(index)];
    }
  }
  else
  {
    if(symbol & 0x8000) // 1 in the MSB position
    {
      psk_bit = 1;
    }
    else // 0 in the MSB position
    {
      psk_bit = 0;
    }
   
    symbol <<= 1;
    
    if(symbol == 0)
    {
      zero_count = 2;
    }
    else
    {
      zero_count = 0;
    }
  }
  
  set_vfo = 1;
}
*/
 
void loop()
{
  if(set_vfo)
  {    
    if(psk_bit)
    {
      psk_one();
    }
    else
    {
      psk_zero();
    }
    
    if(symbol == 0)
    {
      if(zero_count)
      {
        psk_bit = 0;
        zero_count--;
      }
      else
      {
        index++;
      
        // Reset message pointer to beginning of string if at end
        if(index >= mystring.length())
        {
          index = 0;
        }
        
        symbol = varicode[mystring.charAt(index)];
      }
    }
    else
    {
      if(symbol & 0x8000) // 1 in the MSB position
      {
        psk_bit = 1;
      }
      else // 0 in the MSB position
      {
        psk_bit = 0;
      }
     
      symbol <<= 1;
      
      if(symbol == 0)
      {
        zero_count = 2;
      }
      else
      {
        zero_count = 0;
      }
    }
    
    set_vfo = 0;
  }
}

void psk_zero()
{
  //si5351.si5351_write(165, 0);
  //si5351.si5351_write(166, 0);
  //si5351.pll_reset(SI5351_PLLA);
  //si5351.set_clock_source(SI5351_CLK0, SI5351_CLK_SRC_CLKIN);
  //si5351.set_clock_source(SI5351_CLK1, SI5351_CLK_SRC_MS);
  //si5351.set_clock_source(SI5351_CLK2, SI5351_CLK_SRC_MS);
  si5351.set_freq((freq * 100ULL) + (baud_rate / 2), pll_freq, SI5351_CLK0);
  si5351.set_freq((freq * 100ULL) - (baud_rate / 2), pll_freq, SI5351_CLK1);
  digitalWrite(led, LOW);
  //si5351.set_phase(SI5351_CLK1, 0);
  //si5351.set_phase(SI5351_CLK2, 0);
  //si5351.si5351_write(16, 0x0c);
  //si5351.si5351_write(17, 0x0c);
}

void psk_one()
{
  //si5351.set_clock_source(SI5351_CLK0, SI5351_CLK_SRC_CLKIN);
  //si5351.set_clock_source(SI5351_CLK1, SI5351_CLK_SRC_MS0);
  //si5351.set_clock_source(SI5351_CLK2, SI5351_CLK_SRC_MS0);
  //si5351.set_phase(SI5351_CLK1, 0);
  //si5351.set_phase(SI5351_CLK2, 0);
  si5351.set_freq((freq * 100ULL), pll_freq, SI5351_CLK0);
  si5351.set_freq((freq * 100ULL), pll_freq, SI5351_CLK1);
  digitalWrite(led, HIGH);
  //si5351.set_phase(SI5351_CLK1, 0);
  //si5351.set_phase(SI5351_CLK2, 0);
  //si5351.si5351_write(16, 0x0c);
  //si5351.si5351_write(17, 0x0c);
}

void ext_clock()
{
  static uint32_t ext_ticks = 0;
  
  ext_ticks++;
  
  if(ext_ticks >= clock_mult)
  {
    set_vfo = 1;
    ext_ticks = 0;
  }
}