Simple JT65 beacon for Arduino driving the Si5351

int.h

/* Stuff specific to the general (integer) version of the Reed-Solomon codecs
 *
 * Copyright 2003, Phil Karn, KA9Q
 * May be used under the terms of the GNU Lesser General Public License (LGPL)
 */
typedef unsigned int data_t;

#define MODNN(x) modnn(rs,x)

#define MM (rs->mm)
#define NN (rs->nn)
#define ALPHA_TO (rs->alpha_to) 
#define INDEX_OF (rs->index_of)
#define GENPOLY (rs->genpoly)
#define NROOTS (rs->nroots)
#define FCR (rs->fcr)
#define PRIM (rs->prim)
#define IPRIM (rs->iprim)
#define PAD (rs->pad)
#define A0 (NN)

rs_common.h

/* Stuff common to all the general-purpose Reed-Solomon codecs
 * Copyright 2004 Phil Karn, KA9Q
 * May be used under the terms of the GNU Lesser General Public License (LGPL)
 */

#include "int.h"

/* Reed-Solomon codec control block */
struct rs {
  int mm;              /* Bits per symbol */
  int nn;              /* Symbols per block (= (1<<mm)-1) */
  data_t *alpha_to;     /* log lookup table */
  data_t *index_of;     /* Antilog lookup table */
  data_t *genpoly;      /* Generator polynomial */
  int nroots;     /* Number of generator roots = number of parity symbols */
  int fcr;        /* First consecutive root, index form */
  int prim;       /* Primitive element, index form */
  int iprim;      /* prim-th root of 1, index form */
  int pad;        /* Padding bytes in shortened block */
};

static inline int modnn(struct rs *rs,int x){
  while (x >= rs->nn) {
    x -= rs->nn;
    x = (x >> rs->mm) + (x & rs->nn);
  }
  return x;
}

Si5351_JT65.ino

//
// Simple JT9 beacon for Arduino, with the Etherkit Si5351A Breakout
// Board, by Jason Milldrum NT7S.
//
// Transmit an abritrary message of up to 13 valid characters
// (a Type 6 message).
// 
// Original code based on Feld Hell beacon for Arduino by Mark 
// Vandewettering K6HX, adapted for the Si5351A by Robert 
// Liesenfeld AK6L <[email protected]>.  Timer setup
// code by Thomas Knutsen LA3PNA.
// 
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject
// to the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
// IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
// ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
// CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

#include <si5351.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include "int.h"
#include "rs_common.h"
#include "Wire.h"

#define TONE_SPACING            269           // ~2.6917 Hz
#define SUBMODE_A               5812         // CTC value for JT65A
#define SYMBOL_COUNT            126

#define LED_PIN                 13

//typedef unsigned int data_t;

// Global variables
Si5351 si5351;
unsigned long freq = 14077100;
char message[14] = "NT7S CN85";
uint8_t tx_buffer[SYMBOL_COUNT];
static void * rs;

// Global variables used in ISRs
volatile bool proceed = false;

/* Reed-Solomon encoder
 * Copyright 2003, Phil Karn, KA9Q
 * May be used under the terms of the GNU Lesser General Public License (LGPL)
 */
void encode_rs_int(void *p,data_t *data, data_t *parity)
{
  struct rs *rs = (struct rs *)p;

#undef A0
#define A0 (NN) /* Special reserved value encoding zero in index form */


  int i, j;
  data_t feedback;

  memset(parity,0,NROOTS*sizeof(data_t));

  for(i=0;i<NN-NROOTS-PAD;i++){
    feedback = INDEX_OF[data[i] ^ parity[0]];
    if(feedback != A0){      /* feedback term is non-zero */
#ifdef UNNORMALIZED
      /* This line is unnecessary when GENPOLY[NROOTS] is unity, as it must
       * always be for the polynomials constructed by init_rs()
       */
      feedback = MODNN(NN - GENPOLY[NROOTS] + feedback);
#endif
      for(j=1;j<NROOTS;j++)
  parity[j] ^= ALPHA_TO[MODNN(feedback + GENPOLY[NROOTS-j])];
    }
    /* Shift */
    memmove(&parity[0],&parity[1],sizeof(data_t)*(NROOTS-1));
    if(feedback != A0)
      parity[NROOTS-1] = ALPHA_TO[MODNN(feedback + GENPOLY[0])];
    else
      parity[NROOTS-1] = 0;
  }
}

void free_rs_int(void *p)
{
  struct rs *rs = (struct rs *)p;

  free(rs->alpha_to);
  free(rs->index_of);
  free(rs->genpoly);
  free(rs);
}

/* Initialize a Reed-Solomon codec
 * symsize = symbol size, bits
 * gfpoly = Field generator polynomial coefficients
 * fcr = first root of RS code generator polynomial, index form
 * prim = primitive element to generate polynomial roots
 * nroots = RS code generator polynomial degree (number of roots)
 * pad = padding bytes at front of shortened block
 */
void *init_rs_int(int symsize,int gfpoly,int fcr,int prim,
  int nroots,int pad){
  struct rs *rs;
  
//#undef NULL
//#define NULL ((void *)0)

  int i, j, sr,root,iprim;

  rs = ((struct rs *)0);
  /* Check parameter ranges */
  if(symsize < 0 || symsize > 8*sizeof(data_t)){
    goto done;
  }

  if(fcr < 0 || fcr >= (1<<symsize))
    goto done;
  if(prim <= 0 || prim >= (1<<symsize))
    goto done;
  if(nroots < 0 || nroots >= (1<<symsize))
    goto done; /* Can't have more roots than symbol values! */
  if(pad < 0 || pad >= ((1<<symsize) -1 - nroots))
    goto done; /* Too much padding */

  rs = (struct rs *)calloc(1,sizeof(struct rs));
  if(rs == NULL)
    goto done;

  rs->mm = symsize;
  rs->nn = (1<<symsize)-1;
  rs->pad = pad;

  rs->alpha_to = (data_t *)malloc(sizeof(data_t)*(rs->nn+1));
  if(rs->alpha_to == NULL){
    free(rs);
    rs = ((struct rs *)0);
    goto done;
  }
  rs->index_of = (data_t *)malloc(sizeof(data_t)*(rs->nn+1));
  if(rs->index_of == NULL){
    free(rs->alpha_to);
    free(rs);
    rs = ((struct rs *)0);
    goto done;
  }

  /* Generate Galois field lookup tables */
  rs->index_of[0] = A0; /* log(zero) = -inf */
  rs->alpha_to[A0] = 0; /* alpha**-inf = 0 */
  sr = 1;
  for(i=0;i<rs->nn;i++){
    rs->index_of[sr] = i;
    rs->alpha_to[i] = sr;
    sr <<= 1;
    if(sr & (1<<symsize))
      sr ^= gfpoly;
    sr &= rs->nn;
  }
  if(sr != 1){
    /* field generator polynomial is not primitive! */
    free(rs->alpha_to);
    free(rs->index_of);
    free(rs);
    rs = ((struct rs *)0);
    goto done;
  }

  /* Form RS code generator polynomial from its roots */
  rs->genpoly = (data_t *)malloc(sizeof(data_t)*(nroots+1));
  if(rs->genpoly == NULL){
    free(rs->alpha_to);
    free(rs->index_of);
    free(rs);
    rs = ((struct rs *)0);
    goto done;
  }
  rs->fcr = fcr;
  rs->prim = prim;
  rs->nroots = nroots;

  /* Find prim-th root of 1, used in decoding */
  for(iprim=1;(iprim % prim) != 0;iprim += rs->nn)
    ;
  rs->iprim = iprim / prim;

  rs->genpoly[0] = 1;
  for (i = 0,root=fcr*prim; i < nroots; i++,root += prim) {
    rs->genpoly[i+1] = 1;

    /* Multiply rs->genpoly[] by  @**(root + x) */
    for (j = i; j > 0; j--){
      if (rs->genpoly[j] != 0)
  rs->genpoly[j] = rs->genpoly[j-1] ^ rs->alpha_to[modnn(rs,rs->index_of[rs->genpoly[j]] + root)];
      else
  rs->genpoly[j] = rs->genpoly[j-1];
    }
    /* rs->genpoly[0] can never be zero */
    rs->genpoly[0] = rs->alpha_to[modnn(rs,rs->index_of[rs->genpoly[0]] + root)];
  }
  /* convert rs->genpoly[] to index form for quicker encoding */
  for (i = 0; i <= nroots; i++)
    rs->genpoly[i] = rs->index_of[rs->genpoly[i]];
 done:;

  return rs;
}

// END KA9Q Reed-Solomon library


// Timer interrupt vector.  This toggles the variable we use to gate
// each column of output to ensure accurate timing.  Called whenever
// Timer1 hits the count set below in setup().
ISR(TIMER1_COMPA_vect)
{
    proceed = true;
}

uint8_t jt_code(char c)
{
  /* Validate the input then return the proper integer code */
  // Return 255 as an error code if the char is not allowed

  if(isdigit(c))
  {
    return (uint8_t)(c - 48);
  }
  else if(c >= 'A' && c <= 'Z')
  {
    return (uint8_t)(c - 55);
  }
  else if(c == ' ')
  {
    return 36;
  }
  else if(c == '+')
  {
    return 37;
  }
  else if(c == '-')
  {
    return 38;
  }
  else if(c == '.')
  {
    return 39;
  }
  else if(c == '/')
  {
    return 40;
  }
  else if(c == '?')
  {
    return 41;
  }
  else
  {
    return 255;
  }
}

uint8_t gray_code(uint8_t c)
{
  return (c >> 1) ^ c;
}

void rs_encode(uint8_t * data, uint8_t * symbols)
{
  unsigned int dat1[12];
  unsigned int b[51];
  unsigned int i;

  // Reverse data order for the Karn codec.
  for(i = 0; i < 12; i++)
  {
    dat1[i] = data[11 - i];
  }
  
  // Compute the parity symbols
  encode_rs_int(rs, dat1, b);

  // Move parity symbols and data into symbols array, in reverse order.
  for (i = 0; i < 51; i++)
  {
    symbols[50-i] = b[i];
  }
  
  for (i = 0; i < 12; i++)
  {
    symbols[i + 51] = dat1[11 - i];
  }
}

void jt65_encode(char * message, uint8_t symbols[SYMBOL_COUNT])
{
  uint8_t i, j, k;
  
  // Convert all chars to uppercase
  for(i = 0; i < 13; i++)
  {
    if(islower(message[i]))
    {
      message[i] = toupper(message[i]);
    }
  }
  
  // Collapse multiple spaces down to one
  
  // Pad the message with trailing spaces
  uint8_t len = strlen(message);
  if(len < 13)
  {
    for(i = len; i < 13; i++)
    {
      message[i] = ' ';
    }
  }
  
  // Bit packing
  // -----------
  uint8_t c[12];
  uint32_t n1, n2, n3;
  
  // Find the N values
  n1 = jt_code(message[0]);
  n1 = n1 * 42 + jt_code(message[1]);
  n1 = n1 * 42 + jt_code(message[2]);
  n1 = n1 * 42 + jt_code(message[3]);
  n1 = n1 * 42 + jt_code(message[4]);
  
  n2 = jt_code(message[5]);
  n2 = n2 * 42 + jt_code(message[6]);
  n2 = n2 * 42 + jt_code(message[7]);
  n2 = n2 * 42 + jt_code(message[8]);
  n2 = n2 * 42 + jt_code(message[9]);
  
  n3 = jt_code(message[10]);
  n3 = n3 * 42 + jt_code(message[11]);
  n3 = n3 * 42 + jt_code(message[12]);
  
  
  // Pack bits 15 and 16 of N3 into N1 and N2,
  // then mask reset of N3 bits
  n1 = (n1 << 1) + ((n3 >> 15) & 1);
  n2 = (n2 << 1) + ((n3 >> 16) & 1);
  n3 = n3 & 0x7fff;
  
  // Set the freeform message flag
  n3 += 32768;
  
  c[0] = (n1 >> 22) & 0x003f;
  c[1] = (n1 >> 16) & 0x003f;
  c[2] = (n1 >> 10) & 0x003f;
  c[3] = (n1 >> 4) & 0x003f;
  c[4] = ((n1 & 0x000f) << 2) + ((n2 >> 26) & 0x0003);
  c[5] = (n2 >> 20) & 0x003f;
  c[6] = (n2 >> 14) & 0x003f;
  c[7] = (n2 >> 8) & 0x003f;
  c[8] = (n2 >> 2) & 0x003f;
  c[9] = ((n2 & 0x0003) << 4) + ((n3 >> 12) & 0x000f);
  c[10] = (n3 >> 6) & 0x003f;
  c[11] = n3 & 0x003f;
  
  // Reed-Solomon encoding
  // ---------------------
  uint8_t s[63];
  k = 0;
  
  rs_encode(c, s);

  // Interleaving
  // ------------
  uint8_t d[63];
  uint8_t d1[7][9];
  
  // Fill temp d1 array
  for(i = 0; i < 9; i++)
  {
    for(j = 0; j < 7; j++)
    {
      d1[i][j] = s[(i * 7) + j];
    }
  }
  
  // Interleave and translate back to 1D destination array
  for(i = 0; i < 7; i++)
  {
    for(j = 0; j < 9; j++)
    {
      d[(i * 9) + j] = d1[j][i];
    }
  }

  // Gray Code
  // ---------
  uint8_t g[63];
  
  for(i = 0; i < 63; i++)
  {
    g[i] = gray_code(d[i]);
  }
  
  // Merge with sync vector
  // ----------------------
  const uint8_t sync_vector[126] =
  {1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 0,
   0, 1, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 1,
   0, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 1,
   0, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1,
   1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1,
   0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1,
   1, 1, 1, 1, 1, 1};
   
  j = 0;
   
  for(i = 0; i < 126; i++)
  {
    if(sync_vector[i])
    {
      symbols[i] = 0;
    }
    else
    {
      symbols[i] = g[j] + 2;
      j++;
    }
  }
  
}
 
// Loop through the string, transmitting one character at a time.
void encode(char * tx_string)
{
    uint8_t i;

    jt65_encode(tx_string, tx_buffer);
    
    // Reset the tone to 0 and turn on the output
    si5351.output_enable(SI5351_CLK0, 1);
    digitalWrite(LED_PIN, HIGH);
    
    // Now do the rest of the message
    for(i = 0; i < SYMBOL_COUNT; i++)
    {
        si5351.set_freq((freq * 100) + (tx_buffer[i] * TONE_SPACING), 0, SI5351_CLK0);
        proceed = false;
        while(!proceed);
    }
        
    // Turn off the output
    si5351.output_enable(SI5351_CLK0, 0);
    digitalWrite(LED_PIN, LOW);
}

 
void setup()
{
  // Use the Arduino's on-board LED as a keying indicator.
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(LED_PIN, LOW);
  //Serial.begin(57600);
      
  // Initialize the Si5351
  // Change the 2nd parameter in init if using a ref osc other
  // than 25 MHz
  si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0);

  // Set CLK0 output
  si5351.set_correction(-6190);
  si5351.set_freq(freq * 100, 0, SI5351_CLK0);
  si5351.drive_strength(SI5351_CLK0, SI5351_DRIVE_8MA); // Set for max power if desired
  si5351.output_enable(SI5351_CLK0, 0); // Disable the clock initially
  
  // Set up Timer1 for interrupts every symbol period.
  noInterrupts();          // Turn off interrupts.
  TCCR1A = 0;              // Set entire TCCR1A register to 0; disconnects
                           //   interrupt output pins, sets normal waveform
                           //   mode.  We're just using Timer1 as a counter.
  TCNT1  = 0;              // Initialize counter value to 0.
  TCCR1B = (1 << CS12) |   // Set CS12 and CS10 bit to set prescale
    (1 << CS10) |          //   to /1024
    (1 << WGM12);          //   turn on CTC
                           //   which gives, 64 us ticks
  TIMSK1 = (1 << OCIE1A);  // Enable timer compare interrupt.
  OCR1A = SUBMODE_A;          // Set up interrupt trigger count;
  interrupts();            // Re-enable interrupts.

  // Initialize the Reed-Solomon encoder
  rs = (struct rs *)(intptr_t)init_rs_int(6, 0x43, 3, 1, 51, 0);

  // Send the message on startup.
  // Needs to be synced to a minute boundary.
  encode(message);
}
 
void loop()
{
  // Nothing
}