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Fix the CCITT16 checksums for CSBK, DMR Data and D-Star Headers.
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@g4klx
g4klx committed Feb 18, 2016
1 parent 9a3fe18 commit 63aa53c
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Showing 8 changed files with 96 additions and 56 deletions.
86 changes: 61 additions & 25 deletions CRC.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,30 @@
#include <cassert>
#include <cmath>

const uint8_t CRC8_TABLE[] = {
0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31,
0x24, 0x23, 0x2A, 0x2D, 0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65,
0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D, 0xE0, 0xE7, 0xEE, 0xE9,
0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD,
0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85, 0xA8, 0xAF, 0xA6, 0xA1,
0xB4, 0xB3, 0xBA, 0xBD, 0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2,
0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA, 0xB7, 0xB0, 0xB9, 0xBE,
0xAB, 0xAC, 0xA5, 0xA2, 0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A,
0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32, 0x1F, 0x18, 0x11, 0x16,
0x03, 0x04, 0x0D, 0x0A, 0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42,
0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A, 0x89, 0x8E, 0x87, 0x80,
0x95, 0x92, 0x9B, 0x9C, 0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4,
0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8,
0xDD, 0xDA, 0xD3, 0xD4, 0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C,
0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44, 0x19, 0x1E, 0x17, 0x10,
0x05, 0x02, 0x0B, 0x0C, 0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34,
0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B, 0x76, 0x71, 0x78, 0x7F,
0x6A, 0x6D, 0x64, 0x63, 0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B,
0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13, 0xAE, 0xA9, 0xA0, 0xA7,
0xB2, 0xB5, 0xBC, 0xBB, 0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83,
0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF,
0xFA, 0xFD, 0xF4, 0xF3, 0x01};

const uint16_t CCITT16_TABLE1[] = {
0x0000U, 0x1189U, 0x2312U, 0x329bU, 0x4624U, 0x57adU, 0x6536U, 0x74bfU,
0x8c48U, 0x9dc1U, 0xaf5aU, 0xbed3U, 0xca6cU, 0xdbe5U, 0xe97eU, 0xf8f7U,
Expand Down Expand Up @@ -142,31 +166,27 @@ unsigned char CCRC::encodeEightBit(const unsigned char *in, unsigned int length)
return crc;
}

bool CCRC::checkCCITT16(const unsigned char *in, unsigned int length)
bool CCRC::checkCCITT162(const unsigned char *in, unsigned int length)
{
assert(in != NULL);
assert(length > 2U);

unsigned short crc16 = 0U;
union {
uint16_t crc16;
uint8_t crc8[2U];
};

for (unsigned int a = 0; a < (length - 2U); a++) {
unsigned char val = in[a];
crc16 = 0U;

for (unsigned int i = 0U; i < 8U; i++) {
bool c15 = (crc16 >> 15 & 0x01U) == 0x01U;
bool bit = (val >> (7 - i) & 0x01U) == 0x01U;
crc16 <<= 1;
if (c15 ^ bit)
crc16 ^= 0x1021U;
}
}
for (unsigned i = 0U; i < (length - 2U); i++)
crc16 = (uint16_t(crc8[0U]) << 8) ^ CCITT16_TABLE2[crc8[1U] ^ in[i]];

LogMessage("CCITT16, %04X == %02X %02X", crc16, in[length - 2U], in[length - 1U]);
crc16 = ~crc16;

return crc16 == (in[length - 2U] << 8 | in[length - 1U]);
return crc8[0U] == in[length - 1U] && crc8[1U] == in[length - 2U];
}

void CCRC::addCCITT16(unsigned char *in, unsigned int length)
void CCRC::addCCITT161(unsigned char *in, unsigned int length)
{
assert(in != NULL);
assert(length > 2U);
Expand All @@ -177,6 +197,7 @@ void CCRC::addCCITT16(unsigned char *in, unsigned int length)
};

crc16 = 0xFFFFU;

for (unsigned int i = 0U; i < (length - 2U); i++)
crc16 = uint16_t(crc8[1U]) ^ CCITT16_TABLE1[crc8[0U] ^ in[i]];

Expand All @@ -186,21 +207,36 @@ void CCRC::addCCITT16(unsigned char *in, unsigned int length)
in[length - 1U] = crc8[1U];
}

bool CCRC::checkCCITT161(const unsigned char *in, unsigned int length)
{
assert(in != NULL);
assert(length > 2U);

union {
uint16_t crc16;
uint8_t crc8[2U];
};

crc16 = 0xFFFFU;

for (unsigned int i = 0U; i < (length - 2U); i++)
crc16 = uint16_t(crc8[1U]) ^ CCITT16_TABLE1[crc8[0U] ^ in[i]];

crc16 = ~crc16;

return crc8[0U] == in[length - 2U] && crc8[1U] == in[length - 1U];
}

unsigned char CCRC::crc8(const unsigned char *in, unsigned int length)
{
unsigned int crc = 0U;
assert(in != NULL);

for (unsigned int j = 0U; j < length; j++, in++) {
crc ^= (*in << 8);
uint32_t crc = 0U;

for (unsigned int i = 0U; i < 8U; i++) {
if (crc & 0x8000U)
crc ^= (0x1070U << 3);
crc <<= 1;
}
}
for (unsigned int i = 0U; i < length; i++)
crc = CRC8_TABLE[uint8_t(crc) ^ in[i]] ^ (crc >> 8);

return crc >> 8;
return crc;
}

bool CCRC::crcFICH(const unsigned char* fich)
Expand Down
6 changes: 4 additions & 2 deletions CRC.h
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Original file line number Diff line number Diff line change
Expand Up @@ -25,8 +25,10 @@ class CCRC
static bool checkFiveBit(bool* in, unsigned int tcrc);
static void encodeFiveBit(const bool* in, unsigned int& tcrc);

static bool checkCCITT16(const unsigned char* in, unsigned int length);
static void addCCITT16(unsigned char* in, unsigned int length);
static void addCCITT161(unsigned char* in, unsigned int length);

static bool checkCCITT161(const unsigned char* in, unsigned int length);
static bool checkCCITT162(const unsigned char* in, unsigned int length);

static unsigned char encodeEightBit(const unsigned char* in, unsigned int length);

Expand Down
4 changes: 3 additions & 1 deletion DMRCSBK.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,9 @@ m_valid(false)
data[10U] ^= CSBK_CRC_MASK[0U];
data[11U] ^= CSBK_CRC_MASK[1U];

m_valid = CCRC::checkCCITT16(data, 12U);
m_valid = CCRC::checkCCITT162(data, 12U);
if (!m_valid)
return;

m_CSBKO = CSBKO(data[0U] & 0x3FU);
m_FID = data[1U];
Expand Down
3 changes: 3 additions & 0 deletions DMRControl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,9 @@ bool CDMRControl::processWakeup(const unsigned char* data)

CDMRCSBK csbk(data + 2U);

if (!csbk.isValid())
return false;

CSBKO csbko = csbk.getCSBKO();
if (csbko != CSBKO_BSDWNACT)
return false;
Expand Down
2 changes: 1 addition & 1 deletion DMRDataHeader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ m_blocks(0U)
header[10U] ^= DATA_HEADER_CRC_MASK[0U];
header[11U] ^= DATA_HEADER_CRC_MASK[1U];

m_valid = CCRC::checkCCITT16(header, 12U);
m_valid = CCRC::checkCCITT162(header, 12U);

m_gi = (header[0U] & 0x80U) == 0x80U;

Expand Down
36 changes: 20 additions & 16 deletions DMRSlot.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -197,10 +197,10 @@ void CDMRSlot::writeModem(unsigned char *data)
return;

CDMRDataHeader dataHeader(data + 2U);
// if (!dataHeader.isValid()) {
// LogMessage("DMR Slot %u: unable to decode the data header", m_slotNo);
// return;
// }
if (!dataHeader.isValid()) {
LogMessage("DMR Slot %u: unable to decode the RF data header", m_slotNo);
return;
}

bool gi = dataHeader.getGI();
unsigned int srcId = dataHeader.getSrcId();
Expand Down Expand Up @@ -241,10 +241,10 @@ void CDMRSlot::writeModem(unsigned char *data)
LogMessage("DMR Slot %u, received RF data header from %u to %s%u, %u blocks", m_slotNo, srcId, gi ? "TG ": "", dstId, m_frames);
} else if (dataType == DT_CSBK) {
CDMRCSBK csbk(data + 2U);
// if (!csbk.isValid()) {
// LogMessage("DMR Slot %u: unable to decode the CSBK", m_slotNo);
// return;
// }
if (!csbk.isValid()) {
LogMessage("DMR Slot %u: unable to decode the RF CSBK", m_slotNo);
return;
}

CSBKO csbko = csbk.getCSBKO();
switch (csbko) {
Expand Down Expand Up @@ -617,10 +617,10 @@ void CDMRSlot::writeNetwork(const CDMRData& dmrData)
return;

CDMRDataHeader dataHeader(data + 2U);
// if (!dataHeader.isValid()) {
// LogMessage("DMR Slot %u: unable to decode the data header", m_slotNo);
// return;
// }
if (!dataHeader.isValid()) {
LogMessage("DMR Slot %u: unable to decode the network data header", m_slotNo);
return;
}

bool gi = dataHeader.getGI();
unsigned int srcId = dataHeader.getSrcId();
Expand Down Expand Up @@ -761,10 +761,10 @@ void CDMRSlot::writeNetwork(const CDMRData& dmrData)
#endif
} else if (dataType == DT_CSBK) {
CDMRCSBK csbk(data + 2U);
// if (!csbk.isValid()) {
// LogMessage("DMR Slot %u: unable to decode the CSBK", m_slotNo);
// return;
// }
if (!csbk.isValid()) {
LogMessage("DMR Slot %u: unable to decode the network CSBK", m_slotNo);
return;
}

CSBKO csbko = csbk.getCSBKO();
switch (csbko) {
Expand Down Expand Up @@ -1023,11 +1023,15 @@ void CDMRSlot::setShortLC(unsigned int slotNo, unsigned int id, FLCO flco, bool

lc[4U] = CCRC::crc8(lc, 4U);

CUtils::dump("Short LC", lc, 5U);

unsigned char sLC[9U];

CDMRShortLC shortLC;
shortLC.encode(lc, sLC);

CUtils::dump("Short LC with FEC", sLC, 9U);

m_modem->writeDMRShortLC(sLC);
}

Expand Down
2 changes: 1 addition & 1 deletion DStarHeader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -136,5 +136,5 @@ void CDStarHeader::get(unsigned char* header) const

::memcpy(header, m_header, DSTAR_HEADER_LENGTH_BYTES);

CCRC::addCCITT16(header, DSTAR_HEADER_LENGTH_BYTES);
CCRC::addCCITT161(header, DSTAR_HEADER_LENGTH_BYTES);
}
13 changes: 3 additions & 10 deletions DStarSlowData.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -82,18 +82,11 @@ CDStarHeader* CDStarSlowData::add(const unsigned char* data)
for (unsigned int i = 3U; i < 39U; i++)
m_header[i] &= 0x7FU;

// Save the CRC for later comparison
unsigned char crc[2U];
::memcpy(crc, m_header + 39U, 2U);

// Add the new CRC
CCRC::addCCITT16(m_header, DSTAR_HEADER_LENGTH_BYTES);

// Compare them
if (::memcmp(crc, m_header + 39U, 2U) != 0) {
// Check the CRC
bool ret = CCRC::checkCCITT161(m_header, DSTAR_HEADER_LENGTH_BYTES);
if (!ret) {
if (m_ptr == 45U)
LogMessage("D-Star, invalid slow data header");
::memcpy(m_header + 39U, crc, 2U);
return NULL;
}

Expand Down

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