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dsd-fme/src/nxdn_deperm.c
lwvmobile 9f624e0b62 NXDN CAC/CCH Messages; Initial Trunking Support;
2022-11-17 05:50:14 -05:00

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//NXDN descramble/deperm/depuncture and utility functions
//Reworked portions from Osmocom OP25
/* -*- c++ -*- */
/*
* NXDN Encoder/Decoder (C) Copyright 2019 Max H. Parke KA1RBI
*
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this software; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "dsd.h"
#include "nxdn_const.h"
static const uint8_t scramble_t[] = { //values are the position values we need to invert in the descramble
2, 5, 6, 7, 10, 12, 14, 16, 17, 22, 23, 25, 26, 27, 28, 30, 33, 34, 36, 37, 38, 41, 45, 47,
52, 54, 56, 57, 59, 62, 63, 64, 65, 66, 67, 69, 70, 73, 76, 79, 81, 82, 84, 85, 86, 87, 88,
89, 92, 95, 96, 98, 100, 103, 104, 107, 108, 116, 117, 121, 122, 125, 127, 131, 132, 134,
137, 139, 140, 141, 142, 143, 144, 145, 147, 151, 153, 154, 158, 159, 160, 162, 164, 165,
168, 170, 171, 174, 175, 176, 177, 181
};
static const int PARITY[] = {
0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 0,
1, 0, 1, 1, 0, 1, 0, 0, 1, 0, 1,
1, 0, 0, 1, 1, 0, 1, 0, 0, 1
};
//decoding functions here
void nxdn_descramble(uint8_t dibits[], int len)
{
for (int i=0; i<sizeof(scramble_t); i++) {
if (scramble_t[i] >= len)
break;
dibits[scramble_t[i]] ^= 0x2; // invert sign of scrambled dibits
}
}
void nxdn_deperm_facch(dsd_opts * opts, dsd_state * state, uint8_t bits[144])
{
uint8_t deperm[144];
uint8_t depunc[192];
uint8_t trellis_buf[96];
uint16_t crc = 0; //crc calculated by function
uint16_t check = 0; //crc from payload for comparison
int out;
char buf[128];
for (int i=0; i<144; i++)
deperm[PERM_16_9[i]] = bits[i];
out = 0;
for (int i=0; i<144; i+=3) {
depunc[out++] = deperm[i+0];
depunc[out++] = 0;
depunc[out++] = deperm[i+1];
depunc[out++] = deperm[i+2];
}
//trellis_decode(trellis_buf, depunc, 92);
//switch to the convolutional decoder
uint8_t temp[210];
uint8_t s0;
uint8_t s1;
uint8_t m_data[13];
memset (temp, 0, sizeof(temp));
memset (m_data, 0, sizeof(m_data));
memset (trellis_buf, 0, sizeof(trellis_buf));
for (int i = 0; i < 192; i++)
{
temp[i] = depunc[i] << 1;
}
for (int i = 0; i < 8; i++)
{
temp[i+192] = 0;
}
CNXDNConvolution_start();
for (int i = 0U; i < 100U; i++)
{
s0 = temp[(2*i)];
s1 = temp[(2*i)+1];
CNXDNConvolution_decode(s0, s1);
}
CNXDNConvolution_chainback(m_data, 96U);
for(int i = 0; i < 12; i++)
{
trellis_buf[(i*8)+0] = (m_data[i] >> 7) & 1;
trellis_buf[(i*8)+1] = (m_data[i] >> 6) & 1;
trellis_buf[(i*8)+2] = (m_data[i] >> 5) & 1;
trellis_buf[(i*8)+3] = (m_data[i] >> 4) & 1;
trellis_buf[(i*8)+4] = (m_data[i] >> 3) & 1;
trellis_buf[(i*8)+5] = (m_data[i] >> 2) & 1;
trellis_buf[(i*8)+6] = (m_data[i] >> 1) & 1;
trellis_buf[(i*8)+7] = (m_data[i] >> 0) & 1;
}
//load tail 16 bits into check variable to compare vs computed crc value
for (int i = 0; i < 12; i++)
{
check = check << 1;
check = check + trellis_buf[80+i];
}
crc = crc12f (trellis_buf, 80);
if (crc == check) NXDN_Elements_Content_decode(opts, state, 1, trellis_buf);
//else if (opts->payload == 1) NXDN_Elements_Content_decode(opts, state, 0, trellis_buf);
if (opts->payload == 1)
{
fprintf (stderr, "\n");
fprintf (stderr, " FACCH Payload ");
for (int i = 0; i < 12; i++)
{
fprintf (stderr, "[%02X]", m_data[i]);
}
fprintf (stderr, " - %03X %03X", crc, check);
}
}
//new sacch
void nxdn_deperm_sacch(dsd_opts * opts, dsd_state * state, uint8_t bits[60])
{
uint8_t deperm[60];
uint8_t depunc[72];
uint8_t trellis_buf[32];
uint8_t answer[26];
int o = 0;
uint8_t crc = 0; //value computed by crc6 on payload
uint8_t check = 0; //value pulled from last 6 bits
int sf = 0;
int ran = 0;
int part_of_frame = 0;
for (int i=0; i<60; i++)
deperm[PERM_12_5[i]] = bits[i];
for (int p=0; p<60; p+= 10) {
depunc[o++] = deperm[p+0];
depunc[o++] = deperm[p+1];
depunc[o++] = deperm[p+2];
depunc[o++] = deperm[p+3];
depunc[o++] = deperm[p+4];
depunc[o++] = 0;
depunc[o++] = deperm[p+5];
depunc[o++] = deperm[p+6];
depunc[o++] = deperm[p+7];
depunc[o++] = deperm[p+8];
depunc[o++] = deperm[p+9];
depunc[o++] = 0;
}
//trellis_decode(trellis_buf, depunc, 32);
//switch to the convolutional decoder
uint8_t temp[90];
uint8_t s0;
uint8_t s1;
uint8_t m_data[5];
memset (temp, 0, sizeof (temp));
memset (m_data, 0, sizeof (m_data));
memset (trellis_buf, 0, sizeof(trellis_buf));
for (int i = 0; i < 72; i++)
{
temp[i] = depunc[i] << 1;
}
for (int i = 0; i < 8; i++)
{
temp[i+72] = 0;
}
CNXDNConvolution_start();
for (int i = 0U; i < 40U; i++)
{
s0 = temp[(2*i)];
s1 = temp[(2*i)+1];
CNXDNConvolution_decode(s0, s1);
}
//stored as 5 bytes, will need to convert to trellis_buf after running
CNXDNConvolution_chainback(m_data, 36U);
for(int i = 0; i < 4; i++)
{
trellis_buf[(i*8)+0] = (m_data[i] >> 7) & 1;
trellis_buf[(i*8)+1] = (m_data[i] >> 6) & 1;
trellis_buf[(i*8)+2] = (m_data[i] >> 5) & 1;
trellis_buf[(i*8)+3] = (m_data[i] >> 4) & 1;
trellis_buf[(i*8)+4] = (m_data[i] >> 3) & 1;
trellis_buf[(i*8)+5] = (m_data[i] >> 2) & 1;
trellis_buf[(i*8)+6] = (m_data[i] >> 1) & 1;
trellis_buf[(i*8)+7] = (m_data[i] >> 0) & 1;
}
crc = crc6(trellis_buf, 32);
for (int i = 0; i < 6; i++)
{
check = check << 1;
check = check + trellis_buf[i+26];
}
//FIRST! If part of a non_superframe, and CRC is good, send directly to NXDN_Elements_Content_decode
if (state->nxdn_sacch_non_superframe == TRUE)
{
if (state->nxdn_last_ran != -1) fprintf (stderr, " RAN %02d ", state->nxdn_last_ran);
else fprintf (stderr, " ");
uint8_t nsf_sacch[26];
memset (nsf_sacch, 0, sizeof(nsf_sacch));
for (int i = 0; i < 26; i++)
{
nsf_sacch[i] = trellis_buf[i+8];
}
if (crc == 0) NXDN_Elements_Content_decode(opts, state, 1, nsf_sacch);
if (opts->payload == 1)
{
fprintf (stderr, "\n SACCH NSF ");
for (int i = 0; i < 5; i++)
{
fprintf (stderr, "[%02X]", m_data[i]);
}
if (crc != 0) fprintf (stderr, " CRC ERR - %02X %02X", crc, check);
}
}
//If part of superframe, collect the fragments and send to NXDN_SACCH_Full_decode instead
else if (state->nxdn_sacch_non_superframe == FALSE)
{
//sf and ran together are denoted as SR in the manual (more confusing acronyms)
//sf (structure field) and RAN will always exist in first 8 bits of each SACCH, then the next 18 bits are the fragment of the superframe
sf = (trellis_buf[0] << 1) | trellis_buf[1];
ran = (trellis_buf[2] << 5) | (trellis_buf[3] << 4) | (trellis_buf[4] << 3) | (trellis_buf[5] << 2) | (trellis_buf[6] << 1) | trellis_buf[7];
if (sf == 3) part_of_frame = 0;
else if (sf == 2) part_of_frame = 1;
else if (sf == 1) part_of_frame = 2;
else if (sf == 0) part_of_frame = 3;
else part_of_frame = 0;
fprintf (stderr, "%s", KCYN);
if (state->nxdn_last_ran != -1) fprintf (stderr, " RAN %02d ", state->nxdn_last_ran);
else fprintf (stderr, " ");
fprintf (stderr, "%s", KNRM);
//reset scrambler seed to key value on new superframe
if (part_of_frame == 0 && state->nxdn_cipher_type == 0x1) state->payload_miN = 0;
if (crc == 0)
{
state->nxdn_ran = state->nxdn_last_ran = ran;
state->nxdn_sf = sf;
state->nxdn_part_of_frame = part_of_frame;
state->nxdn_sacch_frame_segcrc[part_of_frame] = 0; //zero indicates good check
}
else state->nxdn_sacch_frame_segcrc[part_of_frame] = 1; //1 indicates bad check
int sacch_segment = 0;
for (int i = 0; i < 18; i++)
{
sacch_segment = sacch_segment << 1;
sacch_segment = sacch_segment + trellis_buf[i+8];
state->nxdn_sacch_frame_segment[part_of_frame][i] = trellis_buf[i+8];
}
//Hand off to LEH NXDN_SACCH_Full_decode
if (part_of_frame == 3)
{
NXDN_SACCH_Full_decode (opts, state);
}
if (opts->payload == 1)
{
fprintf (stderr, "\n");
fprintf (stderr, " SACCH SF Segment #%d ", part_of_frame+1);
for (int i = 0; i < 5; i++)
{
fprintf (stderr, "[%02X]", m_data[i]);
}
if (crc != 0) fprintf (stderr, " CRC ERR - %02X %02X", crc, check);
}
}
}
void nxdn_deperm_facch2_udch(dsd_opts * opts, dsd_state * state, uint8_t bits[348])
{
uint8_t deperm[348];
uint8_t depunc[406];
uint8_t trellis_buf[199];
int id = 0;
uint16_t crc = 0;
for (int i=0; i<348; i++) {
deperm[PERM_12_29[i]] = bits[i];
}
for (int i=0; i<29; i++) {
depunc[id++] = deperm[i*12];
depunc[id++] = deperm[i*12+1];
depunc[id++] = deperm[i*12+2];
depunc[id++] = 0;
depunc[id++] = deperm[i*12+3];
depunc[id++] = deperm[i*12+4];
depunc[id++] = deperm[i*12+5];
depunc[id++] = deperm[i*12+6];
depunc[id++] = deperm[i*12+7];
depunc[id++] = deperm[i*12+8];
depunc[id++] = deperm[i*12+9];
depunc[id++] = 0;
depunc[id++] = deperm[i*12+10];
depunc[id++] = deperm[i*12+11];
}
//trellis_decode(trellis_buf, depunc, 199);
//switch to the convolutional decoder
uint8_t temp[220];
uint8_t s0;
uint8_t s1;
uint8_t m_data[26];
memset (trellis_buf, 0, sizeof(trellis_buf));
memset (temp, 0, sizeof (temp));
memset (m_data, 0, sizeof (m_data));
for (int i = 0; i < 406; i++)
{
temp[i] = depunc[i] << 1;
}
for (int i = 0; i < 8; i++)
{
temp[i+203] = 0;
}
CNXDNConvolution_start();
for (int i = 0U; i < 207U; i++)
{
s0 = temp[(2*i)];
s1 = temp[(2*i)+1];
CNXDNConvolution_decode(s0, s1);
}
//numerals seem okay now
CNXDNConvolution_chainback(m_data, 203U);
for(int i = 0; i < 26; i++)
{
trellis_buf[(i*8)+0] = (m_data[i] >> 7) & 1;
trellis_buf[(i*8)+1] = (m_data[i] >> 6) & 1;
trellis_buf[(i*8)+2] = (m_data[i] >> 5) & 1;
trellis_buf[(i*8)+3] = (m_data[i] >> 4) & 1;
trellis_buf[(i*8)+4] = (m_data[i] >> 3) & 1;
trellis_buf[(i*8)+5] = (m_data[i] >> 2) & 1;
trellis_buf[(i*8)+6] = (m_data[i] >> 1) & 1;
trellis_buf[(i*8)+7] = (m_data[i] >> 0) & 1;
}
crc = crc15(trellis_buf, 199);
fprintf (stderr, " F2/U ");
if (crc == 0) NXDN_Elements_Content_decode(opts, state, 1, trellis_buf);
if (opts->payload == 1)
{
fprintf (stderr, "\n");
fprintf (stderr, " F2/U Payload\n ");
for (int i = 0; i < 26; i++)
{
fprintf (stderr, "[%02X]", m_data[i]);
if (i == 12) fprintf (stderr, "\n ");
}
if (crc != 0) fprintf (stderr, " CRC ERR ");
}
}
void nxdn_deperm_cac(dsd_opts * opts, dsd_state * state, uint8_t bits[300])
{
uint8_t deperm[300];
uint8_t depunc[350];
uint8_t trellis_buf[171];
int id = 0;
uint16_t crc = 0;
for (int i=0; i<300; i++) {
deperm[PERM_12_25[i]] = bits[i];
}
for (int i=0; i<25; i++) {
depunc[id++] = deperm[i*12];
depunc[id++] = deperm[i*12+1];
depunc[id++] = deperm[i*12+2];
depunc[id++] = 0;
depunc[id++] = deperm[i*12+3];
depunc[id++] = deperm[i*12+4];
depunc[id++] = deperm[i*12+5];
depunc[id++] = deperm[i*12+6];
depunc[id++] = deperm[i*12+7];
depunc[id++] = deperm[i*12+8];
depunc[id++] = deperm[i*12+9];
depunc[id++] = 0;
depunc[id++] = deperm[i*12+10];
depunc[id++] = deperm[i*12+11];
}
//trellis_decode(trellis_buf, depunc, 171);
//switch to the convolutional decoder
uint8_t temp[360];
uint8_t s0;
uint8_t s1;
uint8_t m_data[26];
memset (trellis_buf, 0, sizeof(trellis_buf));
memset (temp, 0, sizeof (temp));
memset (m_data, 0, sizeof (m_data));
for (int i = 0; i < 350; i++)
{
temp[i] = depunc[i] << 1;
}
for (int i = 0; i < 8; i++)
{
temp[i+350] = 0;
}
CNXDNConvolution_start();
for (int i = 0U; i < 179U; i++)
{
s0 = temp[(2*i)];
s1 = temp[(2*i)+1];
CNXDNConvolution_decode(s0, s1);
}
CNXDNConvolution_chainback(m_data, 175U);
for(int i = 0; i < 22; i++)
{
trellis_buf[(i*8)+0] = (m_data[i] >> 7) & 1;
trellis_buf[(i*8)+1] = (m_data[i] >> 6) & 1;
trellis_buf[(i*8)+2] = (m_data[i] >> 5) & 1;
trellis_buf[(i*8)+3] = (m_data[i] >> 4) & 1;
trellis_buf[(i*8)+4] = (m_data[i] >> 3) & 1;
trellis_buf[(i*8)+5] = (m_data[i] >> 2) & 1;
trellis_buf[(i*8)+6] = (m_data[i] >> 1) & 1;
trellis_buf[(i*8)+7] = (m_data[i] >> 0) & 1;
}
crc = crc16cac(trellis_buf, 171);
fprintf (stderr, " CAC ");
//message type will probably be neccesary beforehand on single/dual meessage runs
//run message, check len, load into a seperate buffer, send to element, do same with other piece?
uint8_t MessageType = 0;
for (int i = 0; i < 6; i++)
{
MessageType = MessageType << 1;
MessageType = MessageType + trellis_buf[i+2]; //double check this on CAC
}
uint8_t cac_message_buffer[171];
memset (cac_message_buffer, 0, sizeof(cac_message_buffer));
//shift the cac_message into the appropriate byte arrangement for element_decoder
for (int i = 0; i < 160; i++) //in future, we can use this to send multiple messages to decoder, if present
{
cac_message_buffer[i] = trellis_buf[i+8];
}
if (crc == 0) NXDN_Elements_Content_decode(opts, state, 1, cac_message_buffer);
if (opts->payload == 1)
{
fprintf (stderr, "\n");
fprintf (stderr, " CAC Payload\n ");
for (int i = 0; i < 22; i++)
{
fprintf (stderr, "[%02X]", m_data[i]);
if (i == 10) fprintf (stderr, "\n ");
}
if (crc != 0) fprintf (stderr, " CRC ERR ");
}
}
void nxdn_message_type (dsd_opts * opts, dsd_state * state, uint8_t MessageType)
{
fprintf (stderr, "%s", KYEL);
if (MessageType == 0x10) fprintf(stderr, " IDLE");
else if (MessageType == 0x11) fprintf(stderr, " DISC"); //disconnect
else if (MessageType == 0x01) fprintf(stderr, " VCALL");
else if (MessageType == 0x03) fprintf(stderr, " VCALL IV");
else if (MessageType == 0x07) fprintf(stderr, " TX_REL_EX");
else if (MessageType == 0x08) fprintf(stderr, " TX_REL");
else if (MessageType == 0x04) fprintf(stderr, " VCALL_ASSGN");
else if (MessageType == 0x05) fprintf(stderr, " VCALL_ASSGN_DUP");
else if (MessageType == 0x0E) fprintf(stderr, " DCALL_ASSGN");
else if (MessageType == 0x18) fprintf(stderr, " SITE_INFO");
else if (MessageType == 0x19) fprintf(stderr, " SRV_INFO");
else if (MessageType == 0x1C) fprintf(stderr, " FAIL_STAT_INFO");
else if (MessageType == 0x1A) fprintf(stderr, " CCH_INFO");
else if (MessageType == 0x1B) fprintf(stderr, " ADJ_SITE_INFO");
else if (MessageType == 0x20) fprintf(stderr, " REG_RESP");
else if (MessageType == 0x22) fprintf(stderr, " REG_C_RESP");
else if (MessageType == 0x24) fprintf(stderr, " GRP_REG_RESP");
else if (MessageType == 0x32) fprintf(stderr, " STAT_REQ");
else if (MessageType == 0x33) fprintf(stderr, " STAT_RESP");
else if (MessageType == 0x38) fprintf(stderr, " SDCALL_REQ_HEADER");
else if (MessageType == 0x39) fprintf(stderr, " SDCALL_REQ_USERDATA");
else if (MessageType == 0x3B) fprintf(stderr, " SDCALL_RESP");
else if (MessageType == 0x3F) fprintf(stderr, " ALIAS");
else if (MessageType == 0x0C) fprintf(stderr, " DCALL_ACK");
else fprintf(stderr, " Unknown M-%02X", MessageType);
fprintf (stderr, "%s", KNRM);
//zero out stale values so they won't persist after a transmit release
//disable if random messages wipe out the alias
if (MessageType == 0x08 || MessageType == 0x10) //idle, tx_rel
{
memset (state->nxdn_alias_block_segment, 0, sizeof(state->nxdn_alias_block_segment));
state->nxdn_last_rid = 0;
state->nxdn_last_tg = 0;
state->nxdn_cipher_type = 0;
memset (state->nxdn_sacch_frame_segcrc, 1, sizeof(state->nxdn_sacch_frame_segcrc));
memset (state->nxdn_sacch_frame_segment, 0, sizeof(state->nxdn_sacch_frame_segment));
sprintf (state->nxdn_call_type, "%s", "");
}
}
//voice descrambler
void LFSRN(char * BufferIn, char * BufferOut, dsd_state * state)
{
int i;
int lfsr;
int pN[49] = {0};
int bit = 0;
lfsr = state->payload_miN & 0x7FFF;
for (i = 0; i < 49; i++)
{
pN[i] = lfsr & 0x1;
bit = ( (lfsr >> 1) ^ (lfsr >> 0) ) & 1;
lfsr = ( (lfsr >> 1 ) | (bit << 14) );
BufferOut[i] = BufferIn[i] ^ pN[i];
}
state->payload_miN = lfsr & 0x7FFF;
}
//utility functions here, consider moving to its own file later
static inline void cfill(uint8_t result[], const uint8_t src[], int len)
{
for (int i=0; i<len; i++)
result[i] = load_i(src+i*8, 8);
}
static inline int load_i(const uint8_t val[], int len) {
int acc = 0;
for (int i=0; i<len; i++){
acc = (acc << 1) + (val[i] & 1);
}
return acc;
}
// trellis_1_2 encode: source is in bits, result in bits
static inline void trellis_encode(uint8_t result[], const uint8_t source[], int result_len, int reg)
{
for (int i=0; i<result_len; i+=2) {
reg = (reg << 1) | source[i>>1];
result[i] = PARITY[reg & 0x19];
result[i+1] = PARITY[reg & 0x17];
}
}
// simplified trellis 2:1 decode; source and result in bits
// assumes that encoding was done with NTEST trailing zero bits
// result_len should be set to the actual number of data bits
// in the original unencoded message (excl. these trailing bits)
static inline void trellis_decode(uint8_t result[], const uint8_t source[], int result_len)
{
int reg = 0;
int min_d;
int min_bt;
static const int NTEST = 4;
static const int NTESTC = 1 << NTEST;
uint8_t bt[NTEST];
uint8_t tt[NTEST*2];
int dstats[4];
int sum;
for (int p=0; p < 4; p++)
dstats[p] = 0;
for (int p=0; p < result_len; p++) {
for (int i=0; i<NTESTC; i++) {
bt[0] = (i&8)>>3;
bt[1] = (i&4)>>2;
bt[2] = (i&2)>>1;
bt[3] = (i&1);
trellis_encode(tt, bt, NTEST*2, reg);
sum=0;
for (int j=0; j<NTEST*2; j++) {
sum += tt[j] ^ source[p*2+j];
}
if (i == 0 || sum < min_d) {
min_d = sum;
min_bt = bt[0];
}
}
result[p] = min_bt;
reg = (reg << 1) | min_bt;
dstats[(min_d > 3) ? 3 : min_d] += 1;
}
// fprintf (stderr, "stats\t%d %d %d %d\n", dstats[0], dstats[1], dstats[2], dstats[3]);
}
static uint8_t crc6(const uint8_t buf[], int len)
{
uint8_t s[6];
uint8_t a;
for (int i=0;i<6;i++)
s[i] = 1;
for (int i=0;i<len;i++) {
a = buf[i] ^ s[0];
s[0] = a ^ s[1];
s[1] = s[2];
s[2] = s[3];
s[3] = a ^ s[4];
s[4] = a ^ s[5];
s[5] = a;
}
return load_i(s, 6);
}
static uint16_t crc12f(const uint8_t buf[], int len)
{
uint8_t s[12];
uint8_t a;
for (int i=0;i<12;i++)
s[i] = 1;
for (int i=0;i<len;i++) {
a = buf[i] ^ s[0];
s[0] = a ^ s[1];
s[1] = s[2];
s[2] = s[3];
s[3] = s[4];
s[4] = s[5];
s[5] = s[6];
s[6] = s[7];
s[7] = s[8];
s[8] = a ^ s[9];
s[9] = a ^ s[10];
s[10] = a ^ s[11];
s[11] = a;
}
return load_i(s, 12);
}
static uint16_t crc15(const uint8_t buf[], int len)
{
uint8_t s[15];
uint8_t a;
for (int i=0;i<15;i++)
s[i] = 1;
for (int i=0;i<len;i++) {
a = buf[i] ^ s[0];
s[0] = a ^ s[1];
s[1] = s[2];
s[2] = s[3];
s[3] = a ^ s[4];
s[4] = a ^ s[5];
s[5] = s[6];
s[6] = s[7];
s[7] = a ^ s[8];
s[8] = a ^ s[9];
s[9] = s[10];
s[10] = s[11];
s[11] = s[12];
s[12] = a ^ s[13];
s[13] = s[14];
s[14] = a;
}
return load_i(s, 15);
}
static uint16_t crc16cac(const uint8_t buf[], int len)
{
int crc = 0xc3ee;
int poly = (1<<12) + (1<<5) + 1;
for (int i=0;i<len;i++) {
crc = ((crc << 1) | buf[i]) & 0x1ffff;
if(crc & 0x10000)
crc = (crc & 0xffff) ^ poly;
}
crc = crc ^ 0xffff;
return crc & 0xffff;
}
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