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M17 - Packet Decoder WIP;

This commit is contained in:
lwvmobile 2024-03-10 01:39:42 -05:00
parent d12f6a1191
commit c1577905cd
5 changed files with 141 additions and 6 deletions
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7
include/dsd.h
View File

@ -812,7 +812,7 @@ typedef struct
* Frame sync patterns
*/
//The inverse of LSF also seems to be Stream Frame Type, only going to work on Stream mode for now
//M17 Sync Patterns
#define M17_LSF "11113313"
#define M17_STR "33331131"
//alternating with last symbol opposite of first symbol of LSF
@ -820,8 +820,8 @@ typedef struct
#define M17_PIV "13131313"
#define M17_PRE_LSF "3131313133331131" //Preamble + LSF
#define M17_PIV_LSF "1313131311113313" //Preamble + LSF
// #define M17_BRT "31331111"
// #define M17_PKT "13113333"
#define M17_BRT "31331111"
#define M17_PKT "13113333"
#define FUSION_SYNC "31111311313113131131"
#define INV_FUSION_SYNC "13333133131331313313"
@ -1016,6 +1016,7 @@ void processDSTAR_HD (dsd_opts * opts, dsd_state * state); //DSTAR Header
void processDSTAR_SD (dsd_opts * opts, dsd_state * state, uint8_t * sd); //DSTAR Slow Data
void processYSF(dsd_opts * opts, dsd_state * state); //YSF
void processM17STR(dsd_opts * opts, dsd_state * state); //M17 (STR)
void processM17PKT(dsd_opts * opts, dsd_state * state); //M17 (PKT)
void processM17LSF(dsd_opts * opts, dsd_state * state); //M17 (LSF)
void encodeM17STR(dsd_opts * opts, dsd_state * state); //M17 (STR) encoder
void encodeM17BRT(dsd_opts * opts, dsd_state * state); //M17 (BRT) encoder

7
src/dsd_dibit.c
View File

@ -267,7 +267,8 @@ int digitize (dsd_opts* opts, dsd_state* state, int symbol)
else if ((state->synctype == 1) || (state->synctype == 3) || (state->synctype == 5) ||
(state->synctype == 9) || (state->synctype == 11) || (state->synctype == 13) ||
(state->synctype == 17) || (state->synctype == 29) || (state->synctype == 31) ||
(state->synctype == 36) || (state->synctype == 99) )
(state->synctype == 77) || (state->synctype == 87) ||(state->synctype == 36) ||
(state->synctype == 99) )
{
// 1 -P25p1
@ -280,6 +281,8 @@ int digitize (dsd_opts* opts, dsd_state* state, int symbol)
// 29 -NXDN (inverted FSW)
// 31 -YSF
// 36 -P25p2
// 77 -M17 BRT
// 87 -M17 PKT
// 99 -M17 Preamble
int valid;
@ -349,6 +352,8 @@ int digitize (dsd_opts* opts, dsd_state* state, int symbol)
// 28 +NXND (FSW)
// 30 +YSF
// 35 +p25p2
// 76 +M17 BRT
// 86 +M17 PKT
// 98 +M17 Preamble
int valid;

8
src/dsd_frame.c
View File

@ -270,12 +270,18 @@ processFrame (dsd_opts * opts, dsd_state * state)
return;
}
//M17
else if ((state->synctype == 16) || (state->synctype == 9) || (state->synctype == 17) || (state->synctype == 8) || (state->synctype == 99) || (state->synctype == 98))
else if ((state->synctype == 16) || (state->synctype == 9) || (state->synctype == 17) || (state->synctype == 8) ||
(state->synctype == 76) || (state->synctype == 77) || (state->synctype == 86) || (state->synctype == 87) ||
(state->synctype == 99) || (state->synctype == 98) )
{
if (state->synctype == 98 || state->synctype == 99) //preamble only
skipDibit(opts, state, 8); //skip dibits to prime the demodulator
else if (state->synctype == 16 || state->synctype == 17)
processM17STR(opts, state);
else if (state->synctype == 76 || state->synctype == 77) {} //Not available yet
// processM17BRT(opts, state); //Not available yet
else if (state->synctype == 86 || state->synctype == 87)
processM17PKT(opts, state);
else
processM17LSF(opts, state);
return;

33
src/dsd_frame_sync.c
View File

@ -613,6 +613,39 @@ getFrameSync (dsd_opts * opts, dsd_state * state)
return (99);
}
}
else if (strcmp(synctest8, M17_PKT) == 0)
{
if (opts->inverted_m17 == 0)
{
printFrameSync (opts, state, "+M17 PKT", synctest_pos + 1, modulation);
state->carrier = 1;
state->offset = synctest_pos;
state->max = ((state->max) + lmax) / 2;
state->min = ((state->min) + lmin) / 2;
if (state->lastsynctype == 86 || state->lastsynctype == 8)
{
state->lastsynctype = 86;
return (86);
}
state->lastsynctype = 86;
fprintf (stderr, "\n");
}
// else //unknown, -BRT?
// {
// printFrameSync (opts, state, "-M17 BRT", synctest_pos + 1, modulation);
// state->carrier = 1;
// state->offset = synctest_pos;
// state->max = ((state->max) + lmax) / 2;
// state->min = ((state->min) + lmin) / 2;
// if (state->lastsynctype == 77)
// {
// state->lastsynctype = 77;
// return (77);
// }
// state->lastsynctype = 77;
// fprintf (stderr, "\n");
// }
}
else if (strcmp(synctest8, M17_STR) == 0)
{
if (opts->inverted_m17 == 0)

92
src/m17.c
View File

@ -2541,4 +2541,94 @@ void encodeM17PKT(dsd_opts * opts, dsd_state * state)
pbc++;
}
}
}
//WIP PKT decoder
void processM17PKT(dsd_opts * opts, dsd_state * state)
{
int i, j, k, x;
uint8_t dbuf[184]; //384-bit (192 symbol) frame - 16-bit (8 symbol) sync pattern (184 dibits)
uint8_t m17_int_bits[368]; //368 bits that are still interleaved
uint8_t m17_rnd_bits[368]; //368 bits that are still scrambled
uint16_t m17_bits[368]; //368 bits that have been de-interleaved and de-scrambled
uint16_t m17_depunc[488]; //488 weighted byte representation of bits after depuncturing
uint8_t pkt_packed[50];
uint8_t pkt_bytes[48];
uint32_t v_err = 0; //errors in viterbi decoder
UNUSED(v_err);
memset (dbuf, 0, sizeof(dbuf));
memset (state->m17_lsf, 0, sizeof(state->m17_lsf));
memset (m17_int_bits, 0, sizeof(m17_int_bits));
memset (m17_bits, 0, sizeof(m17_bits));
memset (m17_rnd_bits, 0, sizeof(m17_rnd_bits));
memset (m17_depunc, 0, sizeof(m17_depunc));
memset (pkt_packed, 0, sizeof(pkt_packed));
memset (pkt_bytes, 0, sizeof(pkt_bytes));
//load dibits into dibit buffer
for (i = 0; i < 184; i++)
dbuf[i] = getDibit(opts, state);
//convert dbuf into a bit array
for (i = 0; i < 184; i++)
{
m17_rnd_bits[i*2+0] = (dbuf[i] >> 1) & 1;
m17_rnd_bits[i*2+1] = (dbuf[i] >> 0) & 1;
}
//descramble the frame
for (i = 0; i < 368; i++)
m17_int_bits[i] = (m17_rnd_bits[i] ^ m17_scramble[i]) & 1;
//deinterleave the bit array using Quadratic Permutation Polynomial
//function π(x) = (45x + 92x^2 ) mod 368
for (i = 0; i < 368; i++)
{
x = ((45*i)+(92*i*i)) % 368;
m17_bits[i] = m17_int_bits[x];
}
//P3 Depuncture and Add Weights
x = 0;
for (i = 0; i < 420; i++)
{
if (p3[i%8] == 1)
m17_depunc[i] = m17_bits[x++];
else m17_depunc[i] = 0;
if (m17_depunc[i])
m17_depunc[i] = 0xFFFF;
else m17_depunc[i] = 0x7FFF;
}
//use the libM17 Viterbi Decoder
uint16_t len = 420;
v_err = viterbi_decode(pkt_bytes, m17_depunc, len);
// v_err -= 3932040; //cost negation (double check this as well as unit, meaning, etc)
//debug
fprintf (stderr, "\n pkt_bytes: \n");
for (i = 0; i < 26; i++)
fprintf (stderr, " %02X", pkt_bytes[i]);
//copy + left shift one octet
memcpy (pkt_packed, pkt_bytes+1, 25);
//Unpack bytes into bits??
//zero out after decoding
memset (state->m17_lsf, 0, sizeof(state->m17_lsf));
//ending linebreak
fprintf (stderr, "\n");
UNUSED(j); UNUSED(k);
} //end processM17LSF