M17 - Simple Packet Encoder;
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lwvmobile
parent
0f5612fdd4
commit
d12f6a1191
324
src/m17.c
324
src/m17.c
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@ -46,6 +46,8 @@ uint8_t p1[62] = {
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1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1
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};
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uint8_t p3[62] = {1, 1, 1, 1, 1, 1, 1, 0};
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//from M17_Implementations / libM17 -- sp5wwp -- should have just looked here to begin with
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//this setup looks very similar to the OP25 variant of crc16, but with a few differences (uses packed bytes)
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uint16_t crc16m17(const uint8_t *in, const uint16_t len)
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@ -2220,7 +2222,323 @@ void encodeM17BRT(dsd_opts * opts, dsd_state * state)
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//encode and create audio of a Project M17 PKT signal
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void encodeM17PKT(dsd_opts * opts, dsd_state * state)
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{
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UNUSED(opts); UNUSED(state);
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//TODO: This whole thing
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fprintf (stderr, "\n M17 Packet (ENCODER): ");
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uint8_t nil[368]; //empty array
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memset (nil, 0, sizeof(nil));
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int i, j, k, x; //basic utility counters
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//User Defined Variables
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uint8_t can = 7; //channel access number
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//numerical representation of dst and src after b40 encoding, or special/reserved value
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unsigned long long int dst = 0;
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unsigned long long int src = 0;
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//DST and SRC Callsign Data (pick up to 9 characters from the b40 char array)
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char d40[] = "BROADCAST"; //DST
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char s40[] = "DSD-FME "; //SRC
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char text[] = "This is a simple text message sent over M17 Packet Data";
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int tlen = strlen((const char*)text)-1; //-1 needed?
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int ptr = 0; //ptr to current position of the text
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int pad = 0; //amount of padding to apply to last frame
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//end User Defined Variables
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//sanity check, tlen cannot exceed maximum len needed for crc and control
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if (tlen > 25*31 - 2) tlen = (25*31)-2;
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//debug tlen value
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fprintf (stderr, " TL: %d", tlen);
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//send dead air with type 99
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for (i = 0; i < 25; i++)
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encodeM17RF (opts, state, nil, 99);
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//send preamble_a for the LSF frame
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encodeM17RF (opts, state, nil, 33);
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//NOTE: PKT mode does not seem to have a format specified by M17 standard,
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//so I will assume that you do not send PKT data over IP to a reflector
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uint8_t m17_lsf[240];
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memset (m17_lsf, 0, sizeof(m17_lsf));
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//Setup LSF Variables, these are not sent in chunks like with voice
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//but only once at start of PKT TX
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uint16_t lsf_ps = 0; //packet or stream indicator bit
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uint16_t lsf_dt = 1; //Data
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uint16_t lsf_et = 0; //encryption type
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uint16_t lsf_es = 0; //encryption sub-type
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uint16_t lsf_cn = can; //can value
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uint16_t lsf_rs = 0; //reserved bits
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//compose the 16-bit frame information from the above sub elements
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uint16_t lsf_fi = 0;
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lsf_fi = (lsf_ps & 1) + (lsf_dt << 1) + (lsf_et << 3) + (lsf_es << 5) + (lsf_cn << 7) + (lsf_rs << 11);
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for (i = 0; i < 16; i++) m17_lsf[96+i] = (lsf_fi >> 15-i) & 1;
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//Convert base40 CSD to numerical values (lifted from libM17)
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//Only if not already set as numerical value
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if (dst == 0)
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{
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for(i = strlen((const char*)d40)-1; i >= 0; i--)
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{
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for(j = 0; j < 40; j++)
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{
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if(d40[i]==b40[j])
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{
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dst=dst*40+j;
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break;
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}
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}
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}
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}
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if (src == 0)
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{
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for(i = strlen((const char*)s40)-1; i >= 0; i--)
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{
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for(j = 0; j < 40; j++)
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{
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if(s40[i]==b40[j])
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{
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src=src*40+j;
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break;
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}
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}
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}
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}
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//end CSD conversion
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//load dst and src values into the LSF
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for (i = 0; i < 48; i++) m17_lsf[i] = (dst >> 47ULL-(unsigned long long int)i) & 1;
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for (i = 0; i < 48; i++) m17_lsf[i+48] = (src >> 47ULL-(unsigned long long int)i) & 1;
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//TODO: Any extra meta fills (extended callsign, etc?)
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//pack and compute the CRC16 for LSF
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uint16_t crc_cmp = 0;
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uint8_t lsf_packed[30];
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memset (lsf_packed, 0, sizeof(lsf_packed));
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for (i = 0; i < 28; i++)
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lsf_packed[i] = (uint8_t)ConvertBitIntoBytes(&m17_lsf[i*8], 8);
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crc_cmp = crc16m17(lsf_packed, 28);
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//attach the crc16 bits to the end of the LSF data
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for (i = 0; i < 16; i++) m17_lsf[224+i] = (crc_cmp >> 15-i) & 1;
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//pack the CRC
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for (i = 28; i < 30; i++)
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lsf_packed[i] = (uint8_t)ConvertBitIntoBytes(&m17_lsf[i*8], 8);
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//Craft and Send Initial LSF frame to be decoded
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//LSF w/ convolutional encoding (double check array sizes)
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uint8_t m17_lsfc[488]; memset (m17_lsfc, 0, sizeof(m17_lsfc));
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//LSF w/ P1 Puncturing
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uint8_t m17_lsfp[368]; memset (m17_lsfp, 0, sizeof(m17_lsfp));
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//LSF w/ Interleave
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uint8_t m17_lsfi[368]; memset (m17_lsfi, 0, sizeof(m17_lsfi));
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//LSF w/ Scrambling
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uint8_t m17_lsfs[368]; memset (m17_lsfs, 0, sizeof(m17_lsfs));
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//Use the convolutional encoder to encode the LSF Frame
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simple_conv_encoder (m17_lsf, m17_lsfc, 244);
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//P1 puncture
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x = 0;
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for (i = 0; i < 488; i++)
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{
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if (p1[i%61] == 1)
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m17_lsfp[x++] = m17_lsfc[i];
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}
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//interleave the bit array using Quadratic Permutation Polynomial
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//function π(x) = (45x + 92x^2 ) mod 368
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for (i = 0; i < 368; i++)
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{
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x = ((45*i)+(92*i*i)) % 368;
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m17_lsfi[x] = m17_lsfp[i];
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}
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//scramble/randomize the frame
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for (i = 0; i < 368; i++)
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m17_lsfs[i] = (m17_lsfi[i] ^ m17_scramble[i]) & 1;
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//a full sized complete packet paylaod to break into smaller frames
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uint8_t m17_p1_full[31*200]; memset (m17_p1_full, 0, sizeof(m17_p1_full));
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//Convert a string text message into UTF-8 octets and load into full
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i = 0; k = 16; //skip first two octets?
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//0x05 is SMS //needed?
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m17_p1_full[5] = 1; m17_p1_full[7] = 1;
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uint8_t cbyte; //byte representation of a single string char
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int block = 0; //number of blocks in total
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for (i = 0; i < tlen; i++)
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{
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cbyte = (uint8_t)text[ptr++];
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for (j = 0; j < 8; j++)
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m17_p1_full[k++] = (cbyte >> 7-j) & 1;
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if (ptr >= tlen) break;
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}
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//end UTF-8 Encoding
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if (ptr >= tlen)
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{
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block = (ptr / 25);
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if (ptr%25) block++;
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pad = (block * 25) - ptr;
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pad -= 2; //subtract two for the CRC
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}
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//debug block, pad, K and ptr position
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fprintf (stderr, " BLOCK: %d; PAD: %d; K: %d; PTR: %d; ", block, pad, k, ptr);
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//Calculate the CRC and attach it here
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uint8_t m17_p1_packed[31*25]; memset (m17_p1_packed, 0, sizeof(m17_p1_packed));
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for (i = 0; i < (25*block)-2; i++)
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m17_p1_packed[i] = (uint8_t)ConvertBitIntoBytes(&m17_p1_full[i*8], 8);
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crc_cmp = crc16m17(m17_p1_packed, (25*block)-2);
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ptr = (block*25*8) - 16;
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//attach the crc16 bits to the end of the LSF data
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for (i = 0; i < 16; i++) m17_p1_full[ptr+i] = (crc_cmp >> 15-i) & 1;
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//debug the full payload
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fprintf (stderr, "\n M17 Packet FULL: ");
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for (i = 0; i < 25*block; i++)
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{
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if ( (i%25) == 0 && i != 0 ) fprintf (stderr, "\n ");
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fprintf (stderr, "%02X", (uint8_t)ConvertBitIntoBytes(&m17_p1_full[i*8], 8));
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}
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//flag to determine if we send a new LSF frame for new encode
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//only send once at the appropriate time when encoder is toggled on
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int new_lsf = 1;
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uint8_t pbc = 1; //packet/octet counter
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uint8_t eot = 0; //end of tx bit
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while (!exitflag)
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{
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//send LSF frame once, if new encode session
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if (new_lsf == 1)
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{
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fprintf (stderr, "\n M17 LSF (ENCODER): ");
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processM17LSF_debug2(opts, state, m17_lsfs);
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//convert bit array into symbols and RF/Audio
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memset (nil, 0, sizeof(nil));
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encodeM17RF (opts, state, nil, 11); //Preamble
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// for (i = 0; i < 6; i++) //test sending multiple LSF OTA
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encodeM17RF (opts, state, m17_lsfs, 1); //LSF
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//flag off after sending
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new_lsf = 0;
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//reset ptr value to use during chunk loading
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ptr = 0;
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}
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//PKT - 206 bits of Packet Data
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uint8_t m17_p1[210]; memset (m17_p1, 0, sizeof(m17_p1));
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//PKT - 420 bits of Packet Data (after Convolutional Encode)
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uint8_t m17_p2c[420]; memset (m17_p2c, 0, sizeof(m17_p2c));
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//PKT - 368 bits of Packet Data (after P2 Puncturing)
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uint8_t m17_p3p[368]; memset (m17_p3p, 0, sizeof(m17_p3p));
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//PKT - 368 bits of Packet Data (after Interleaving)
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uint8_t m17_p4i[368]; memset (m17_p4i, 0, sizeof(m17_p4i));
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//PKT - 368 bits of Packet Data (after Scrambling)
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uint8_t m17_p4s[368]; memset (m17_p4s, 0, sizeof(m17_p4s));
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//Break the full payload into 25 octet chunks and load into p1
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for (i = 0; i < 200; i++)
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m17_p1[i] = m17_p1_full[ptr++];
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//Trigger EOT when out of data to encode
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if (ptr/8 >= tlen)
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{
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eot = 1;
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pbc = 25-2-pad; //set to total minus pad minus crc
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}
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m17_p1[200] = eot;
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//set pbc counter to last 5 bits
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for (i = 0; i < 5; i++)
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m17_p1[201+i] = (pbc >> 4-i) & 1;
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//Use the convolutional encoder to encode the packet data
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simple_conv_encoder (m17_p1, m17_p2c, 210); //206 + 4 trailing bits
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//P3 puncture
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x = 0;
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for (i = 0; i < 420; i++)
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{
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if (p3[i%8] == 1)
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m17_p3p[x++] = m17_p2c[i];
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}
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//debug X bit positions
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// fprintf (stderr, " X: %d", x);
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//interleave the bit array using Quadratic Permutation Polynomial
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//function π(x) = (45x + 92x^2 ) mod 368
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for (i = 0; i < 368; i++)
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{
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x = ((45*i)+(92*i*i)) % 368;
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m17_p4i[x] = m17_p3p[i];
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}
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//scramble/randomize the frame
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for (i = 0; i < 368; i++)
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m17_p4s[i] = (m17_p4i[i] ^ m17_scramble[i]) & 1;
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//debug insert 3 random bit flip in the finished PKT frame
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// int rnd1 = rand()%368;
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// int rnd2 = rand()%368;
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// int rnd3 = rand()%368;
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// m17_b4s[rnd1] ^= 1;
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// m17_b4s[rnd2] ^= 1;
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// m17_b4s[rnd3] ^= 1;
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//-----------------------------------------
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fprintf (stderr, "\n M17 Packet (ENCODER): ");
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//Dump Output of the current Packet Frame
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for (i = 0; i < 26; i++)
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fprintf (stderr, "%02X", (uint8_t)ConvertBitIntoBytes(&m17_p1[i*8], 8));
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//convert bit array into symbols and RF/Audio
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encodeM17RF (opts, state, m17_p4s, 4);
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//send the EOT Marker and some dead air
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if (eot)
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{
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memset (nil, 0, sizeof(nil));
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encodeM17RF (opts, state, nil, 55); //EOT Marker
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//send dead air with type 99
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for (i = 0; i < 25; i++)
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encodeM17RF (opts, state, nil, 99);
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//shut it down
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exitflag = 1;
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}
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//increment packet / byte counter
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pbc++;
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}
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}
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