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MMDVM
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Clean up the M17 synchronisation logic.

This commit is contained in:
Jonathan Naylor 2021-01-02 12:24:11 +00:00
parent bada4d9285
commit 7e919b12f7
3 changed files with 30 additions and 38 deletions
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60
M17RX.cpp
View File

@ -26,10 +26,11 @@
const q15_t SCALING_FACTOR = 18750; // Q15(0.55)
const uint8_t MAX_SYNC_BIT_START_ERRS = 1U;
const uint8_t MAX_SYNC_BIT_RUN_ERRS = 3U;
const uint8_t MAX_SYNC_BIT_START_ERRS = 0U;
const uint8_t MAX_SYNC_BIT_RUN_ERRS = 2U;
const uint8_t MAX_SYNC_SYMBOLS_ERRS = 2U;
const uint8_t MAX_SYNC_SYMBOL_START_ERRS = 0U;
const uint8_t MAX_SYNC_SYMBOL_RUN_ERRS = 1U;
const uint8_t BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U};
@ -102,8 +103,8 @@ void CM17RX::samples(const q15_t* samples, uint16_t* rssi, uint8_t length)
m_buffer[m_dataPtr] = sample;
switch (m_state) {
case M17RXS_HEADER:
processHeader(sample);
case M17RXS_LINK_SETUP:
processLinkSetup(sample);
break;
case M17RXS_STREAM:
processStream(sample);
@ -128,9 +129,9 @@ void CM17RX::samples(const q15_t* samples, uint16_t* rssi, uint8_t length)
void CM17RX::processNone(q15_t sample)
{
bool ret1 = correlateSync(M17_LINK_SETUP_SYNC_SYMBOLS, M17_LINK_SETUP_SYNC_SYMBOLS_VALUES, M17_LINK_SETUP_SYNC_BYTES);
bool ret2 = correlateSync(M17_STREAM_SYNC_SYMBOLS, M17_STREAM_SYNC_SYMBOLS_VALUES, M17_STREAM_SYNC_BYTES);
bool ret3 = correlateSync(M17_PACKET_SYNC_SYMBOLS, M17_PACKET_SYNC_SYMBOLS_VALUES, M17_PACKET_SYNC_BYTES);
bool ret1 = correlateSync(M17_LINK_SETUP_SYNC_SYMBOLS, M17_LINK_SETUP_SYNC_SYMBOLS_VALUES, M17_LINK_SETUP_SYNC_BYTES, MAX_SYNC_SYMBOL_START_ERRS, MAX_SYNC_BIT_START_ERRS);
bool ret2 = correlateSync(M17_STREAM_SYNC_SYMBOLS, M17_STREAM_SYNC_SYMBOLS_VALUES, M17_STREAM_SYNC_BYTES, MAX_SYNC_SYMBOL_START_ERRS, MAX_SYNC_BIT_START_ERRS);
bool ret3 = correlateSync(M17_PACKET_SYNC_SYMBOLS, M17_PACKET_SYNC_SYMBOLS_VALUES, M17_PACKET_SYNC_BYTES, MAX_SYNC_SYMBOL_START_ERRS, MAX_SYNC_BIT_START_ERRS);
if (ret1 || ret2 || ret3) {
// On the first sync, start the countdown to the state change
@ -145,7 +146,7 @@ void CM17RX::processNone(q15_t sample)
m_countdown = 5U;
if (ret1) m_nextState = M17RXS_HEADER;
if (ret1) m_nextState = M17RXS_LINK_SETUP;
if (ret2) m_nextState = M17RXS_STREAM;
if (ret3) m_nextState = M17RXS_PACKET;
}
@ -168,16 +169,8 @@ void CM17RX::processNone(q15_t sample)
}
}
void CM17RX::processHeader(q15_t sample)
void CM17RX::processLinkSetup(q15_t sample)
{
if (m_minSyncPtr < m_maxSyncPtr) {
if (m_dataPtr >= m_minSyncPtr && m_dataPtr <= m_maxSyncPtr)
correlateSync(M17_LINK_SETUP_SYNC_SYMBOLS, M17_LINK_SETUP_SYNC_SYMBOLS_VALUES, M17_LINK_SETUP_SYNC_BYTES);
} else {
if (m_dataPtr >= m_minSyncPtr || m_dataPtr <= m_maxSyncPtr)
correlateSync(M17_LINK_SETUP_SYNC_SYMBOLS, M17_LINK_SETUP_SYNC_SYMBOLS_VALUES, M17_LINK_SETUP_SYNC_BYTES);
}
if (m_dataPtr == m_endPtr) {
m_minSyncPtr = m_syncPtr + M17_FRAME_LENGTH_SAMPLES - 1U;
if (m_minSyncPtr >= M17_FRAME_LENGTH_SAMPLES)
@ -189,7 +182,7 @@ void CM17RX::processHeader(q15_t sample)
calculateLevels(m_startPtr, M17_FRAME_LENGTH_SYMBOLS);
DEBUG4("M17RX: header sync found pos/centre/threshold", m_syncPtr, m_centreVal, m_thresholdVal);
DEBUG4("M17RX: link setup sync found pos/centre/threshold", m_syncPtr, m_centreVal, m_thresholdVal);
uint8_t frame[M17_FRAME_LENGTH_BYTES + 3U];
samplesToBits(m_startPtr, M17_FRAME_LENGTH_SYMBOLS, frame, 8U, m_centreVal, m_thresholdVal);
@ -197,8 +190,13 @@ void CM17RX::processHeader(q15_t sample)
m_lostCount--;
frame[0U] = 0x01U;
writeRSSIHeader(frame);
m_state = M17RXS_NONE;
m_maxCorr = 0;
m_state = M17RXS_NONE;
m_endPtr = NOENDPTR;
m_averagePtr = NOAVEPTR;
m_countdown = 0U;
m_nextState = M17RXS_NONE;
m_maxCorr = 0;
}
}
@ -206,10 +204,10 @@ void CM17RX::processStream(q15_t sample)
{
if (m_minSyncPtr < m_maxSyncPtr) {
if (m_dataPtr >= m_minSyncPtr && m_dataPtr <= m_maxSyncPtr)
correlateSync(M17_STREAM_SYNC_SYMBOLS, M17_STREAM_SYNC_SYMBOLS_VALUES, M17_STREAM_SYNC_BYTES);
correlateSync(M17_STREAM_SYNC_SYMBOLS, M17_STREAM_SYNC_SYMBOLS_VALUES, M17_STREAM_SYNC_BYTES, MAX_SYNC_SYMBOL_RUN_ERRS, MAX_SYNC_BIT_RUN_ERRS);
} else {
if (m_dataPtr >= m_minSyncPtr || m_dataPtr <= m_maxSyncPtr)
correlateSync(M17_STREAM_SYNC_SYMBOLS, M17_STREAM_SYNC_SYMBOLS_VALUES, M17_STREAM_SYNC_BYTES);
correlateSync(M17_STREAM_SYNC_SYMBOLS, M17_STREAM_SYNC_SYMBOLS_VALUES, M17_STREAM_SYNC_BYTES, MAX_SYNC_SYMBOL_RUN_ERRS, MAX_SYNC_BIT_RUN_ERRS);
}
if (m_dataPtr == m_endPtr) {
@ -260,10 +258,10 @@ void CM17RX::processPacket(q15_t sample)
{
if (m_minSyncPtr < m_maxSyncPtr) {
if (m_dataPtr >= m_minSyncPtr && m_dataPtr <= m_maxSyncPtr)
correlateSync(M17_PACKET_SYNC_SYMBOLS, M17_PACKET_SYNC_SYMBOLS_VALUES, M17_PACKET_SYNC_BYTES);
correlateSync(M17_PACKET_SYNC_SYMBOLS, M17_PACKET_SYNC_SYMBOLS_VALUES, M17_PACKET_SYNC_BYTES, MAX_SYNC_SYMBOL_RUN_ERRS, MAX_SYNC_BIT_RUN_ERRS);
} else {
if (m_dataPtr >= m_minSyncPtr || m_dataPtr <= m_maxSyncPtr)
correlateSync(M17_PACKET_SYNC_SYMBOLS, M17_PACKET_SYNC_SYMBOLS_VALUES, M17_PACKET_SYNC_BYTES);
correlateSync(M17_PACKET_SYNC_SYMBOLS, M17_PACKET_SYNC_SYMBOLS_VALUES, M17_PACKET_SYNC_BYTES, MAX_SYNC_SYMBOL_RUN_ERRS, MAX_SYNC_BIT_RUN_ERRS);
}
if (m_dataPtr == m_endPtr) {
@ -310,9 +308,9 @@ void CM17RX::processPacket(q15_t sample)
}
}
bool CM17RX::correlateSync(uint8_t syncSymbols, const int8_t* syncSymbolValues, const uint8_t* syncBytes)
bool CM17RX::correlateSync(uint8_t syncSymbols, const int8_t* syncSymbolValues, const uint8_t* syncBytes, uint8_t maxSymbolErrs, uint8_t maxBitErrs)
{
if (countBits8(m_bitBuffer[m_bitPtr] ^ syncSymbols) <= MAX_SYNC_SYMBOLS_ERRS) {
if (countBits8(m_bitBuffer[m_bitPtr] ^ syncSymbols) <= maxSymbolErrs) {
uint16_t ptr = m_dataPtr + M17_FRAME_LENGTH_SAMPLES - M17_SYNC_LENGTH_SAMPLES + M17_RADIO_SYMBOL_LENGTH;
if (ptr >= M17_FRAME_LENGTH_SAMPLES)
ptr -= M17_FRAME_LENGTH_SAMPLES;
@ -364,17 +362,11 @@ bool CM17RX::correlateSync(uint8_t syncSymbols, const int8_t* syncSymbolValues,
uint8_t sync[M17_SYNC_BYTES_LENGTH];
samplesToBits(startPtr, M17_SYNC_LENGTH_SYMBOLS, sync, 0U, m_centreVal, m_thresholdVal);
uint8_t maxErrs;
if (m_state == M17RXS_NONE)
maxErrs = MAX_SYNC_BIT_START_ERRS;
else
maxErrs = MAX_SYNC_BIT_RUN_ERRS;
uint8_t errs = 0U;
for (uint8_t i = 0U; i < M17_SYNC_BYTES_LENGTH; i++)
errs += countBits8(sync[i] ^ syncBytes[i]);
if (errs <= maxErrs) {
if (errs <= maxBitErrs) {
m_maxCorr = corr;
m_lostCount = MAX_SYNC_FRAMES;
m_syncPtr = m_dataPtr;

6
M17RX.h
View File

@ -27,7 +27,7 @@
enum M17RX_STATE {
M17RXS_NONE,
M17RXS_HEADER,
M17RXS_LINK_SETUP,
M17RXS_STREAM,
M17RXS_PACKET
};
@ -64,10 +64,10 @@ private:
uint16_t m_rssiCount;
void processNone(q15_t sample);
void processHeader(q15_t sample);
void processLinkSetup(q15_t sample);
void processStream(q15_t sample);
void processPacket(q15_t sample);
bool correlateSync(uint8_t syncSymbols, const int8_t* syncSymbolValues, const uint8_t* syncBytes);
bool correlateSync(uint8_t syncSymbols, const int8_t* syncSymbolValues, const uint8_t* syncBytes, uint8_t maxSymbolErrs, uint8_t maxBitErrs);
void calculateLevels(uint16_t start, uint16_t count);
void samplesToBits(uint16_t start, uint16_t count, uint8_t* buffer, uint16_t offset, q15_t centre, q15_t threshold);
void writeRSSIHeader(uint8_t* data);

2
Version.h
View File

@ -19,7 +19,7 @@
#if !defined(VERSION_H)
#define VERSION_H
#define VERSION "20210101"
#define VERSION "20210102"
#endif