Hi Andy and all,
Sorry that I don't have a good document on the format, but
here is the code used to generate it; I hope that it is
enough info for you to build something compatible with WOLF.
You can run WOLF in the "EEPROM" mode to see if a given
message encoding matches your software. If you have trouble,
let me know and I'll try to help.
Transmission involves radix-40 encode, convolutional encode,
interleave, and reference bit insertion.
#define MSGLEN 15 /* source message len in chars */
#define MSGLENW 5 /* radix 40 message len in 16-bit words */
#define WLEN 16 /* bits in 3-character coded group */
#define MSGLENB 80 /* message length in bits */
#define RRATE 6 /* reciprocal of code rate */
/* Radix-40 encoder */
/* Future versions may use codes >=64000 for
control functions, CRC, etc. */
/* in: ASCII string, up to 15 chars
out: array of 16 bit words, radix-40 encoded */
void encr40(char *in, ushort out[])
{
int ch, fill, val, i;
fill = 0;
val = 0;
for (i = 0; i < MSGLEN; ++i) {
if (fill)
ch = 0;
else if (!(ch = *in++))
fill = 1;
else if (ch >= 'A' && ch <= 'Z')
ch = ch - 'A' + 1;
else if (ch >= 'a' && ch <= 'z')
ch = ch - 'a' + 1;
else if (ch >= '0' && ch <= '9')
ch = ch - '0' + 27;
else if (ch == ' ')
ch = 0;
else if (ch == '.')
ch = 37;
else if (ch == '/')
ch = 38;
else
ch = 39;
val = val * 40 + ch;
if (i % 3 == 2) {
*out++ = val;
val = 0;
}
}
}
/* These values are bit-reversed from those in the NASA paper
because the register shifts left */
int cnvcod[] = {042631, 047245, 073363, 056507, 077267, 064537};
/* tail-biting encoder
in: array of radix-40 encoded 16 bit words
out: baseband signal in xmit order, array of chars */
void enccnv(ushort in[], char out[])
{
int sr, i, j, k, b, t;
sr = in[MSGLENW-1]; /* init sr to last 15 bits */
for (i = 0; i < MSGLENW; ++i) {
for (j = 0; j < WLEN; ++j) {
sr = (sr << 1) | (in[i] >> (15-j)) & 1;
for (k = 0; k < RRATE; ++k) {
b = 0;
for (t = sr & cnvcod[k]; t; t &= t-1)
b ^= 1;
/* store */
#if INTLV
out[k*MSGLENB + (j&7)*10 + ((j&8)>>3) + i*2] = b;
#else
out[k*MSGLENB + j + i*WLEN] = b;
#endif
}
}
}
}
char pnpat[] = {
0,0,1,1,1,1,1,0,1,0,1,0,1,1,0,0,0,0,1,1,0,1,0,1,1,0,0,1,0,1,0,0,1,0,0,0,1,0,0,1,
1,0,1,0,0,0,0,0,1,1,1,0,1,0,1,0,1,1,1,0,0,0,1,0,1,1,0,0,0,1,0,1,1,1,1,0,1,0,1,1,
1,1,0,0,1,0,0,0,1,0,0,1,1,1,0,1,0,1,0,0,0,1,0,1,1,0,0,0,1,0,1,0,1,1,0,1,1,0,1,0,
1,0,1,1,0,0,0,0,0,1,0,1,1,0,1,1,0,1,0,0,0,1,0,1,1,1,0,0,0,1,1,1,1,0,1,1,1,0,0,1,
1,0,1,1,0,1,0,0,1,1,1,0,1,0,0,1,1,0,1,0,1,0,0,1,0,0,0,1,1,1,0,1,0,0,1,0,0,0,1,1,
0,0,1,0,1,0,1,1,1,1,0,1,0,1,0,0,0,0,0,0,0,0,0,0,1,0,1,1,1,1,1,1,0,1,1,0,0,1,1,1,
1,1,0,1,0,0,1,0,1,0,1,0,1,1,0,1,0,0,1,0,1,0,0,0,1,0,1,0,1,1,0,0,0,0,0,0,0,0,0,0,
1,1,1,1,1,1,0,1,0,1,1,0,0,1,0,0,1,1,0,1,0,1,1,0,1,1,1,0,0,1,0,1,0,1,0,1,1,1,1,0,
1,1,0,0,1,0,0,0,0,0,0,1,1,1,1,1,0,0,1,1,0,0,0,1,1,1,1,1,0,1,0,0,0,0,0,0,1,0,0,1,
0,1,0,0,0,1,1,0,0,1,0,1,0,1,0,0,1,1,0,1,1,1,0,0,1,1,1,0,0,1,1,1,1,1,0,1,1,0,1,0,
1,0,0,1,1,1,0,0,0,0,0,1,0,0,1,0,1,0,0,0,0,1,1,0,0,0,0,1,1,0,1,0,1,1,1,0,1,0,1,1,
1,0,0,0,1,1,1,1,1,0,0,0,1,1,0,1,0,0,1,1,1,1,1,1,0,1,0,0,1,0,0,1,0,1,0,0,0,1,1,1,
};
Notes: The interleave function is far from optimum but a lot better than
nothing. The PN pattern was chosen literally at random, selecting for low
autocorrelation and for low autocorrelation with short substrings, but is
also far from optimum. I would greatly appreciate it if you find a good
replacement pattern.
Hope this is useful.
73,
Stewart KK7KA
----- Original Message -----
From: "Talbot Andrew" <[email protected]>
To: <[email protected]>
Sent: Thursday, March 22, 2001 7:02 AM
Subject: LF: RE: Re: WOLF - Transmit?
I would like add Wolf coding to my PIC based BPSK generator.
Stuart, can you reveal the exact coding details, I can't find them in
any of the documentation on the Web. Just a comment that the mesage
data is interleaved (?) with a PN Sequence to assist clock recovery and
timing.
Andy G4JNT
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