Update for latest M17 specification.

M17Defines.h

@@ -30,18 +30,29 @@ const unsigned int M17_SYNC_LENGTH_BITS    = 16U;
 const unsigned int M17_SYNC_LENGTH_SYMBOLS = M17_SYNC_LENGTH_BITS / 2U;
 const unsigned int M17_SYNC_LENGTH_SAMPLES = M17_SYNC_LENGTH_SYMBOLS * M17_RADIO_SYMBOL_LENGTH;
 
-const uint8_t M17_SYNC_BYTES[]      = {0x32U, 0x43U};
+const uint8_t M17_HEADER_SYNC_BYTES[] = {0x5DU, 0xDDU};
+const uint8_t M17_DATA_SYNC_BYTES[]   = {0xDDU, 0xDDU};
+
 const uint8_t M17_SYNC_BYTES_LENGTH = 2U;
 
-const uint16_t M17_SYNC_BITS      = 0x3243U;
+const uint16_t M17_HEADER_SYNC_BITS = 0x5DDDU;
+const uint16_t M17_DAYA_SYNC_BITS   = 0xDDDDU;
 
-// 3     2      4      3
+// 5     D      D      D
-// 00 11 00 10  01 00  00 11
+// 01 01 11 01  11 01  11 01
-// +1 -3 +1 -1  +3 +1  +1 -3
+// +3 +3 -3 +3  -3 +3  -3 +3
 
-const int8_t M17_SYNC_SYMBOLS_VALUES[] = {+1, -3, +1, -1, +3, +1, +1, -3};
+const int8_t M17_HEADER_SYNC_SYMBOLS_VALUES[] = {+3, +3, -3, +3, -3, +3, -3, +3};
 
-const uint8_t M17_SYNC_SYMBOLS = 0xAEU;
+const uint8_t M17_HEADER_SYNC_SYMBOLS = 0xD5U;
+
+// D     D      D      D
+// 11 01 11 01  11 01  11 01
+// -3 +3 -3 +3  -3 +3  -3 +3
+
+const int8_t M17_DATA_SYNC_SYMBOLS_VALUES[] = {-3, +3, -3, +3, -3, +3, -3, +3};
+
+const uint8_t M17_DATA_SYNC_SYMBOLS = 0x55U;
 
 #endif
 

M17RX.cpp

@@ -55,6 +55,7 @@ m_maxSyncPtr(NOENDPTR),
 m_maxCorr(0),
 m_lostCount(0U),
 m_countdown(0U),
+m_nextState(M17RXS_NONE),
 m_centre(),
 m_centreVal(0),
 m_threshold(),
@@ -81,6 +82,7 @@ void CM17RX::reset()
   m_thresholdVal = 0;
   m_lostCount    = 0U;
   m_countdown    = 0U;
+  m_nextState    = M17RXS_NONE;
   m_rssiAccum    = 0U;
   m_rssiCount    = 0U;
 }
@@ -100,6 +102,9 @@ 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);
+      break;
     case M17RXS_DATA:
       processData(sample);
       break;
@@ -120,8 +125,10 @@ void CM17RX::samples(const q15_t* samples, uint16_t* rssi, uint8_t length)
 
 void CM17RX::processNone(q15_t sample)
 {
-  bool ret = correlateSync();
+  bool ret1 = correlateSync(M17_HEADER_SYNC_SYMBOLS, M17_HEADER_SYNC_SYMBOLS_VALUES, M17_HEADER_SYNC_BYTES);
-  if (ret) {
+  bool ret2 = correlateSync(M17_DATA_SYNC_SYMBOLS, M17_DATA_SYNC_SYMBOLS_VALUES, M17_DATA_SYNC_BYTES);
+
+  if (ret1 || ret2) {
     // On the first sync, start the countdown to the state change
     if (m_countdown == 0U) {
       m_rssiAccum = 0U;
@@ -133,6 +140,8 @@ void CM17RX::processNone(q15_t sample)
       m_averagePtr = NOAVEPTR;
 
       m_countdown = 5U;
+      
+      m_nextState = ret1 ? M17RXS_HEADER : M17RXS_DATA;
     }
   }
 
@@ -148,19 +157,53 @@ void CM17RX::processNone(q15_t sample)
     if (m_maxSyncPtr >= M17_FRAME_LENGTH_SAMPLES)
       m_maxSyncPtr -= M17_FRAME_LENGTH_SAMPLES;
 
-    m_state      = M17RXS_DATA;
+    m_state      = m_nextState;
     m_countdown  = 0U;
   }
 }
 
+void CM17RX::processHeader(q15_t sample)
+{
+  if (m_minSyncPtr < m_maxSyncPtr) {
+    if (m_dataPtr >= m_minSyncPtr && m_dataPtr <= m_maxSyncPtr)
+      correlateSync(M17_HEADER_SYNC_SYMBOLS, M17_HEADER_SYNC_SYMBOLS_VALUES, M17_HEADER_SYNC_BYTES);
+  } else {
+    if (m_dataPtr >= m_minSyncPtr || m_dataPtr <= m_maxSyncPtr)
+      correlateSync(M17_HEADER_SYNC_SYMBOLS, M17_HEADER_SYNC_SYMBOLS_VALUES, M17_HEADER_SYNC_BYTES);
+  }
+
+  if (m_dataPtr == m_endPtr) {
+    m_minSyncPtr = m_syncPtr + M17_FRAME_LENGTH_SAMPLES - 1U;
+    if (m_minSyncPtr >= M17_FRAME_LENGTH_SAMPLES)
+      m_minSyncPtr -= M17_FRAME_LENGTH_SAMPLES;
+
+    m_maxSyncPtr = m_syncPtr + 1U;
+    if (m_maxSyncPtr >= M17_FRAME_LENGTH_SAMPLES)
+      m_maxSyncPtr -= M17_FRAME_LENGTH_SAMPLES;
+
+    calculateLevels(m_startPtr, M17_FRAME_LENGTH_SYMBOLS);
+
+    DEBUG4("M17RX: header 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);
+
+    m_lostCount--;
+    frame[0U] = 0x01U;
+    writeRSSIHeader(frame);
+    m_state   = M17RXS_DATA;
+    m_maxCorr = 0;
+  }
+}
+
 void CM17RX::processData(q15_t sample)
 {
   if (m_minSyncPtr < m_maxSyncPtr) {
     if (m_dataPtr >= m_minSyncPtr && m_dataPtr <= m_maxSyncPtr)
-      correlateSync();
+      correlateSync(M17_DATA_SYNC_SYMBOLS, M17_DATA_SYNC_SYMBOLS_VALUES, M17_DATA_SYNC_BYTES);
   } else {
     if (m_dataPtr >= m_minSyncPtr || m_dataPtr <= m_maxSyncPtr)
-      correlateSync();
+      correlateSync(M17_DATA_SYNC_SYMBOLS, M17_DATA_SYNC_SYMBOLS_VALUES, M17_DATA_SYNC_BYTES);
   }
 
   if (m_dataPtr == m_endPtr) {
@@ -177,7 +220,7 @@ void CM17RX::processData(q15_t sample)
 
     calculateLevels(m_startPtr, M17_FRAME_LENGTH_SYMBOLS);
 
-    DEBUG4("M17RX: sync found pos/centre/threshold", m_syncPtr, m_centreVal, m_thresholdVal);
+    DEBUG4("M17RX: data 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);
@@ -196,6 +239,7 @@ void CM17RX::processData(q15_t sample)
       m_endPtr     = NOENDPTR;
       m_averagePtr = NOAVEPTR;
       m_countdown  = 0U;
+      m_nextState  = M17RXS_NONE;
       m_maxCorr    = 0;
     } else {
       frame[0U] = m_lostCount == (MAX_SYNC_FRAMES - 1U) ? 0x01U : 0x00U;
@@ -205,9 +249,9 @@ void CM17RX::processData(q15_t sample)
   }
 }
 
-bool CM17RX::correlateSync()
+bool CM17RX::correlateSync(uint8_t syncSymbols, const int8_t* syncSymbolValues, const uint8_t* syncBytes)
 {
-  if (countBits8(m_bitBuffer[m_bitPtr] ^ M17_SYNC_SYMBOLS) <= MAX_SYNC_SYMBOLS_ERRS) {
+  if (countBits8(m_bitBuffer[m_bitPtr] ^ syncSymbols) <= MAX_SYNC_SYMBOLS_ERRS) {
     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;
@@ -224,7 +268,7 @@ bool CM17RX::correlateSync()
       if (val < min)
         min = val;
 
-      switch (M17_SYNC_SYMBOLS_VALUES[i]) {
+      switch (syncSymbolValues[i]) {
       case +3:
         corr -= (val + val + val);
         break;
@@ -267,7 +311,7 @@ bool CM17RX::correlateSync()
 
       uint8_t errs = 0U;
       for (uint8_t i = 0U; i < M17_SYNC_BYTES_LENGTH; i++)
-        errs += countBits8(sync[i] ^ M17_SYNC_BYTES[i]);
+        errs += countBits8(sync[i] ^ syncBytes[i]);
 
       if (errs <= maxErrs) {
         m_maxCorr   = corr;
@@ -385,6 +429,27 @@ void CM17RX::samplesToBits(uint16_t start, uint16_t count, uint8_t* buffer, uint
   }
 }
 
+void CM17RX::writeRSSIHeader(uint8_t* data)
+{
+#if defined(SEND_RSSI_DATA)
+  if (m_rssiCount > 0U) {
+    uint16_t rssi = m_rssiAccum / m_rssiCount;
+
+    data[121U] = (rssi >> 8) & 0xFFU;
+    data[122U] = (rssi >> 0) & 0xFFU;
+
+    serial.writeM17Header(data, M17_FRAME_LENGTH_BYTES + 3U);
+  } else {
+    serial.writeM17Header(data, M17_FRAME_LENGTH_BYTES + 1U);
+  }
+#else
+  serial.writeM17Header(data, M17_FRAME_LENGTH_BYTES + 1U);
+#endif
+
+  m_rssiAccum = 0U;
+  m_rssiCount = 0U;
+}
+
 void CM17RX::writeRSSIData(uint8_t* data)
 {
 #if defined(SEND_RSSI_DATA)

M17RX.h

@@ -27,6 +27,7 @@
 
 enum M17RX_STATE {
   M17RXS_NONE,
+  M17RXS_HEADER,
   M17RXS_DATA
 };
 
@@ -52,6 +53,7 @@ private:
   q31_t       m_maxCorr;
   uint16_t    m_lostCount;
   uint8_t     m_countdown;
+  M17RX_STATE m_nextState;
   q15_t       m_centre[16U];
   q15_t       m_centreVal;
   q15_t       m_threshold[16U];
@@ -61,10 +63,12 @@ private:
   uint16_t    m_rssiCount;
 
   void processNone(q15_t sample);
+  void processHeader(q15_t sample);
   void processData(q15_t sample);
-  bool correlateSync();
+  bool correlateSync(uint8_t syncSymbols, const int8_t* syncSymbolValues, const uint8_t* syncBytes);
   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);
   void writeRSSIData(uint8_t* data);
 };
 

SerialPort.cpp

@@ -63,8 +63,9 @@ const uint8_t MMDVM_P25_LOST     = 0x32U;
 const uint8_t MMDVM_NXDN_DATA    = 0x40U;
 const uint8_t MMDVM_NXDN_LOST    = 0x41U;
 
-const uint8_t MMDVM_M17_DATA     = 0x45U;
+const uint8_t MMDVM_M17_HEADER   = 0x45U;
-const uint8_t MMDVM_M17_LOST     = 0x46U;
+const uint8_t MMDVM_M17_DATA     = 0x46U;
+const uint8_t MMDVM_M17_LOST     = 0x47U;
 
 const uint8_t MMDVM_POCSAG_DATA  = 0x50U;
 
@@ -1257,6 +1258,20 @@ void CSerialPort::processMessage(uint8_t type, const uint8_t* buffer, uint16_t l
 #endif
 
 #if defined(MODE_M17)
+    case MMDVM_M17_HEADER:
+      if (m_m17Enable) {
+        if (m_modemState == STATE_IDLE || m_modemState == STATE_M17)
+          err = m17TX.writeData(buffer, length);
+      }
+      if (err == 0U) {
+        if (m_modemState == STATE_IDLE)
+          setMode(STATE_M17);
+      } else {
+        DEBUG2("Received invalid M17 header", err);
+        sendNAK(err);
+      }
+      break;
+
     case MMDVM_M17_DATA:
       if (m_m17Enable) {
         if (m_modemState == STATE_IDLE || m_modemState == STATE_M17)
@@ -1621,6 +1636,29 @@ void CSerialPort::writeNXDNLost()
 #endif
 
 #if defined(MODE_M17)
+void CSerialPort::writeM17Header(const uint8_t* data, uint8_t length)
+{
+  if (m_modemState != STATE_M17 && m_modemState != STATE_IDLE)
+    return;
+
+  if (!m_m17Enable)
+    return;
+
+  uint8_t reply[130U];
+
+  reply[0U] = MMDVM_FRAME_START;
+  reply[1U] = 0U;
+  reply[2U] = MMDVM_M17_HEADER;
+
+  uint8_t count = 3U;
+  for (uint8_t i = 0U; i < length; i++, count++)
+    reply[count] = data[i];
+
+  reply[1U] = count;
+
+  writeInt(1U, reply, count);
+}
+
 void CSerialPort::writeM17Data(const uint8_t* data, uint8_t length)
 {
   if (m_modemState != STATE_M17 && m_modemState != STATE_IDLE)

SerialPort.h

@@ -65,6 +65,7 @@ public:
 #endif
 
 #if defined(MODE_M17)
+  void writeM17Header(const uint8_t* data, uint8_t length);
   void writeM17Data(const uint8_t* data, uint8_t length);
   void writeM17Lost();
 #endif

Version.h

@@ -19,7 +19,7 @@
 #if !defined(VERSION_H)
 #define  VERSION_H
 
-#define VERSION "20201120"
+#define VERSION "20201126"
 
 #endif