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M17: CRC16 code cleanup

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This commit is contained in:
f4exb 2022-07-27 18:15:47 +02:00
parent 22539b331f
commit a035c42762
4 changed files with 27 additions and 15 deletions
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28
modemm17/CRC16.h
View File

@ -9,23 +9,28 @@
namespace modemm17 namespace modemm17
{ {
template <uint16_t Poly = 0x5935, uint16_t Init = 0xFFFF>
struct CRC16 struct CRC16
{ {
static constexpr uint16_t MASK = 0xFFFF; static const uint16_t MASK = 0xFFFF;
static constexpr uint16_t LSB = 0x0001; static const uint16_t LSB = 0x0001;
static constexpr uint16_t MSB = 0x8000; static const uint16_t MSB = 0x8000;
uint16_t reg_ = Init;
CRC16(uint16_t poly = 0x5935, uint16_t init = 0xFFFF) :
poly_(poly),
init_(init)
{
reg_ = init_;
}
void reset() void reset()
{ {
reg_ = Init; reg_ = init_;
for (size_t i = 0; i != 16; ++i) for (size_t i = 0; i != 16; ++i)
{ {
auto bit = reg_ & LSB; auto bit = reg_ & LSB;
if (bit) reg_ ^= Poly; if (bit) reg_ ^= poly_;
reg_ >>= 1; reg_ >>= 1;
if (bit) reg_ |= MSB; if (bit) reg_ |= MSB;
} }
@ -44,7 +49,7 @@ struct CRC16
{ {
auto msb = reg & MSB; auto msb = reg & MSB;
reg = ((reg << 1) & MASK) | ((byte >> (7 - i)) & LSB); reg = ((reg << 1) & MASK) | ((byte >> (7 - i)) & LSB);
if (msb) reg ^= Poly; if (msb) reg ^= poly_;
} }
return reg & MASK; return reg & MASK;
} }
@ -56,7 +61,7 @@ struct CRC16
{ {
auto msb = reg & MSB; auto msb = reg & MSB;
reg = ((reg << 1) & MASK); reg = ((reg << 1) & MASK);
if (msb) reg ^= Poly; if (msb) reg ^= poly_;
} }
return reg; return reg;
} }
@ -67,6 +72,11 @@ struct CRC16
std::array<uint8_t, 2> result{uint8_t((crc >> 8) & 0xFF), uint8_t(crc & 0xFF)}; std::array<uint8_t, 2> result{uint8_t((crc >> 8) & 0xFF), uint8_t(crc & 0xFF)};
return result; return result;
} }
private:
uint16_t poly_;
uint16_t init_;
uint16_t reg_;
}; };
} // modemm17 } // modemm17

3
modemm17/M17FrameDecoder.h
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@ -45,7 +45,7 @@ struct M17FrameDecoder
PolynomialInterleaver<45, 92, 368> interleaver_; PolynomialInterleaver<45, 92, 368> interleaver_;
Trellis<4,2> trellis_{makeTrellis<4, 2>({031,027})}; Trellis<4,2> trellis_{makeTrellis<4, 2>({031,027})};
Viterbi<decltype(trellis_), 4> viterbi_{trellis_}; Viterbi<decltype(trellis_), 4> viterbi_{trellis_};
CRC16<0x5935, 0xFFFF> crc_; CRC16 crc_;
enum class State { LSF, STREAM, BASIC_PACKET, FULL_PACKET, BERT }; enum class State { LSF, STREAM, BASIC_PACKET, FULL_PACKET, BERT };
enum class SyncWordType { LSF, STREAM, PACKET, BERT }; enum class SyncWordType { LSF, STREAM, PACKET, BERT };
@ -106,6 +106,7 @@ struct M17FrameDecoder
uint8_t lich_segments{0}; ///< one bit per received LICH fragment. uint8_t lich_segments{0}; ///< one bit per received LICH fragment.
M17FrameDecoder(callback_t callback) : M17FrameDecoder(callback_t callback) :
crc_(0x5935, 0xFFFF),
callback_(callback) callback_(callback)
{} {}

9
modemm17/M17Modulator.h
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@ -51,7 +51,7 @@ public:
static const std::array<uint8_t, 2> BERT_SYNC_WORD; static const std::array<uint8_t, 2> BERT_SYNC_WORD;
static const std::array<uint8_t, 2> EOT_SYNC; static const std::array<uint8_t, 2> EOT_SYNC;
static constexpr int8_t bits_to_symbol(uint8_t bits) static int8_t bits_to_symbol(uint8_t bits)
{ {
switch (bits) switch (bits)
{ {
@ -120,7 +120,7 @@ public:
M17Randomizer<368> randomizer; M17Randomizer<368> randomizer;
PolynomialInterleaver<45, 92, 368> interleaver; PolynomialInterleaver<45, 92, 368> interleaver;
CRC16<0x5935, 0xFFFF> crc; CRC16 crc(0x5935, 0xFFFF);
auto rit = std::copy(dest_.begin(), dest_.end(), lsf.begin()); auto rit = std::copy(dest_.begin(), dest_.end(), lsf.begin());
std::copy(source_.begin(), source_.end(), rit); std::copy(source_.begin(), source_.end(), rit);
@ -457,7 +457,8 @@ public:
source_(encode_callsign(source)), source_(encode_callsign(source)),
dest_(encode_callsign(dest)), dest_(encode_callsign(dest)),
can_(10), can_(10),
rrc(makeFirFilter(rrc_taps)) rrc(makeFirFilter(rrc_taps)),
crc_(0x5935, 0xFFFF)
{ {
gnss_.fill(0); gnss_.fill(0);
gnss_on_ = false; gnss_on_ = false;
@ -511,7 +512,7 @@ private:
uint8_t can_; uint8_t can_;
BaseFirFilter<150> rrc; BaseFirFilter<150> rrc;
static const std::array<float, 150> rrc_taps; static const std::array<float, 150> rrc_taps;
CRC16<0x5935, 0xFFFF> crc_; CRC16 crc_;
static LinkSetupFrame::encoded_call_t encode_callsign(std::string callsign) static LinkSetupFrame::encoded_call_t encode_callsign(std::string callsign)
{ {

2
plugins/channelrx/demodm17/m17demodprocessor.cpp
View File

@ -321,7 +321,7 @@ bool M17DemodProcessor::decode_packet(modemm17::M17FrameDecoder::packet_buffer_t
qDebug() << "M17DemodProcessor::decode_packet: last chunk size:" << packet_size << " packet size:" << m_currentPacket.size(); qDebug() << "M17DemodProcessor::decode_packet: last chunk size:" << packet_size << " packet size:" << m_currentPacket.size();
} }
modemm17::CRC16<0x5935, 0xFFFF> crc16; modemm17::CRC16 crc16(0x5935, 0xFFFF);
crc16.reset(); crc16.reset();
for (std::vector<uint8_t>::const_iterator it = m_currentPacket.begin(); it != m_currentPacket.end() - 2; ++it) { for (std::vector<uint8_t>::const_iterator it = m_currentPacket.begin(); it != m_currentPacket.end() - 2; ++it) {