Improving D-Star detection

DMRDMORX.cpp

@@ -209,6 +209,8 @@ void CDMRDMORX::correlateSync()
   m_endPtr = m_dataPtr + DMR_SLOT_TYPE_LENGTH_BITS / 2U + DMR_INFO_LENGTH_BITS / 2U;
   if (m_endPtr >= DMO_BUFFER_LENGTH_BITS)
     m_endPtr -= DMO_BUFFER_LENGTH_BITS;
+    
+  m_modeTimerCnt = 0;
 
   //DEBUG4("SYNC MS Data found pos/start/end:", m_dataPtr, m_startPtr, m_endPtr);
   } else if ( (countBits64((m_patternBuffer & DMR_SYNC_BITS_MASK) ^ DMR_MS_VOICE_SYNC_BITS) <= MAX_SYNC_BYTES_ERRS) || \
@@ -225,6 +227,8 @@ void CDMRDMORX::correlateSync()
   if (m_endPtr >= DMO_BUFFER_LENGTH_BITS)
     m_endPtr -= DMO_BUFFER_LENGTH_BITS;
 
+  m_modeTimerCnt = 0;
+  
   //DEBUG4("SYNC MS Voice found pos/start/end: ", m_dataPtr, m_startPtr, m_endPtr);
   }
 }

DStarRX.cpp

@@ -30,6 +30,11 @@ const unsigned int SYNC_POS        = 21U * DSTAR_DATA_LENGTH_BITS;
 const unsigned int SYNC_SCAN_START = SYNC_POS - 3U;
 const unsigned int SYNC_SCAN_END   = SYNC_POS + 3U;
 
+// D-Star preamble sequence (only 32 bits of 101010...)
+const uint32_t PREAMBLE_MASK = 0xFFFFFFFFU;
+const uint32_t PREAMBLE_DATA = 0xAAAAAAAAU;
+const uint8_t  PREAMBLE_ERRS = 2U;
+
 // D-Star bit order version of 0x55 0x55 0x6E 0x0A
 const uint32_t FRAME_SYNC_DATA = 0x00557650U;
 const uint32_t FRAME_SYNC_MASK = 0x00FFFFFFU;
@@ -284,9 +289,21 @@ void CDStarRX::processNone(bool bit)
   if (bit)
     m_patternBuffer |= 0x01U;
 
+  // Fuzzy matching of the preamble sync sequence
+  if (countBits32((m_patternBuffer & PREAMBLE_MASK) ^ PREAMBLE_DATA) <= PREAMBLE_ERRS) {
+    DEBUG1("DStarRX: preamble detected, fuzzy");
+
+    // Extend scan period in D-Star, once preamble is detected
+    m_modeTimerCnt = 0;
+
+    m_rxState = DSRXS_NONE;
+
+    return;
+  }
+
   // Fuzzy matching of the frame sync sequence
   if (countBits32((m_patternBuffer & FRAME_SYNC_MASK) ^ FRAME_SYNC_DATA) <= FRAME_SYNC_ERRS) {
-    DEBUG1("DStarRX: found frame sync in None");
+    DEBUG1("DStarRX: found frame sync in None, fuzzy");
 
     ::memset(m_rxBuffer, 0x00U, DSTAR_FEC_SECTION_LENGTH_BYTES);
     m_rxBufferBits = 0U;
@@ -297,7 +314,7 @@ void CDStarRX::processNone(bool bit)
 
   // Exact matching of the data sync bit sequence
   if (countBits32((m_patternBuffer & DATA_SYNC_MASK) ^ DATA_SYNC_DATA) == 0U) {
-    DEBUG1("DStarRX: found data sync in None");
+    DEBUG1("DStarRX: found data sync in None, exact");
     
     io.setDecode(true);
 

Globals.h

@@ -53,6 +53,8 @@ const uint16_t RX_RINGBUFFER_SIZE = 120U;
 extern MMDVM_STATE m_modemState;
 extern MMDVM_STATE m_modemState_prev;
 
+extern uint32_t m_modeTimerCnt;
+
 extern bool m_dstarEnable;
 extern bool m_dmrEnable;
 extern bool m_ysfEnable;

IO.cpp

@@ -32,7 +32,6 @@ m_txBuffer(TX_RINGBUFFER_SIZE),
 m_LoDevYSF(false),
 m_ledCount(0U),
 m_scanEnable(false),
-m_modeTimerCnt(0U),
 m_scanPauseCnt(0U),
 m_scanPos(0U),
 m_ledValue(true),
@@ -57,6 +56,8 @@ m_watchdog(0U)
   SCLK_pin(LOW);
   SDATA_pin(LOW);
   SLE_pin(LOW);
+  
+  m_modeTimerCnt = 0;
 }
 
 void CIO::process()

IO.h

@@ -113,7 +113,6 @@ private:
   bool               m_LoDevYSF;
   uint32_t           m_ledCount;
   bool               m_scanEnable;
-  uint32_t           m_modeTimerCnt;
   uint32_t           m_scanPauseCnt;
   uint8_t            m_scanPos;
   uint8_t            m_TotalModes;

MMDVM_HS.cpp

@@ -29,6 +29,8 @@
 MMDVM_STATE m_modemState = STATE_IDLE;
 MMDVM_STATE m_modemState_prev = STATE_IDLE;
 
+uint32_t m_modeTimerCnt;
+
 bool m_dstarEnable = true;
 bool m_dmrEnable   = true;
 bool m_ysfEnable   = true;

MMDVM_HS.ino

@@ -25,6 +25,8 @@
 MMDVM_STATE m_modemState = STATE_IDLE;
 MMDVM_STATE m_modemState_prev = STATE_IDLE;
 
+uint32_t m_modeTimerCnt;
+
 bool m_dstarEnable = true;
 bool m_dmrEnable   = true;
 bool m_ysfEnable   = true;