Merge branch 'FM' into dstar_correlator_fm

Fixes erroneous end sync seen on station having QSB

CalDStarRX.cpp

@@ -24,7 +24,7 @@
 const unsigned int BUFFER_LENGTH = 200U;
 
 const uint32_t PLLMAX = 0x10000U;
-const uint32_t PLLINC = PLLMAX / DSTAR_RADIO_BIT_LENGTH;
+const uint32_t PLLINC = PLLMAX / DSTAR_RADIO_SYMBOL_LENGTH;
 const uint32_t INC    = PLLINC / 32U;
 
 // D-Star bit order version of 0x55 0x2D 0x16

DStarDefines.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2009-2015 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2009-2015,2017 by Jonathan Naylor G4KLX
  *
  *   This program is free software; you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -19,30 +19,50 @@
 #if !defined(DSTARDEFINES_H)
 #define  DSTARDEFINES_H
 
-const unsigned int DSTAR_RADIO_BIT_LENGTH = 5U;      // At 24 kHz sample rate
+const unsigned int DSTAR_RADIO_SYMBOL_LENGTH = 5U;      // At 24 kHz sample rate
 
-const unsigned int DSTAR_HEADER_LENGTH_BYTES = 41U;
-const unsigned int DSTAR_HEADER_LENGTH_BITS  = DSTAR_HEADER_LENGTH_BYTES * 8U;
+const unsigned int DSTAR_HEADER_LENGTH_BYTES   = 41U;
 
-const unsigned int DSTAR_FEC_SECTION_LENGTH_BYTES = 83U;
-const unsigned int DSTAR_FEC_SECTION_LENGTH_BITS  = 660U;
+const unsigned int DSTAR_FEC_SECTION_LENGTH_BYTES   = 83U;
+const unsigned int DSTAR_FEC_SECTION_LENGTH_SYMBOLS = 660U;
+const unsigned int DSTAR_FEC_SECTION_LENGTH_SAMPLES = DSTAR_FEC_SECTION_LENGTH_SYMBOLS * DSTAR_RADIO_SYMBOL_LENGTH;
 
-const unsigned int DSTAR_DATA_LENGTH_BYTES = 12U;
-const unsigned int DSTAR_DATA_LENGTH_BITS  = DSTAR_DATA_LENGTH_BYTES * 8U;
+const unsigned int DSTAR_DATA_LENGTH_BYTES   = 12U;
+const unsigned int DSTAR_DATA_LENGTH_SYMBOLS = DSTAR_DATA_LENGTH_BYTES * 8U;
+const unsigned int DSTAR_DATA_LENGTH_SAMPLES = DSTAR_DATA_LENGTH_SYMBOLS * DSTAR_RADIO_SYMBOL_LENGTH;
 
-const uint8_t      DSTAR_EOT_BYTES[] = {0x55, 0x55, 0x55, 0x55, 0xC8, 0x7A, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
-const unsigned int DSTAR_EOT_LENGTH_BYTES = 6U;
-const unsigned int DSTAR_EOT_LENGTH_BITS  = DSTAR_EOT_LENGTH_BYTES * 8U;
+const unsigned int DSTAR_END_SYNC_LENGTH_BYTES = 6U;
+const unsigned int DSTAR_END_SYNC_LENGTH_BITS  = DSTAR_END_SYNC_LENGTH_BYTES * 8U;
 
-const uint8_t      DSTAR_DATA_SYNC_LENGTH_BYTES = 3U;
-const uint8_t      DSTAR_DATA_SYNC_LENGTH_BITS  = DSTAR_DATA_SYNC_LENGTH_BYTES * 8U;
+const unsigned int DSTAR_FRAME_SYNC_LENGTH_BYTES   = 3U;
+const unsigned int DSTAR_FRAME_SYNC_LENGTH_SYMBOLS = DSTAR_FRAME_SYNC_LENGTH_BYTES * 8U;
+const unsigned int DSTAR_FRAME_SYNC_LENGTH_SAMPLES = DSTAR_FRAME_SYNC_LENGTH_SYMBOLS * DSTAR_RADIO_SYMBOL_LENGTH;
 
-const uint8_t      DSTAR_DATA_SYNC_BYTES[] = {0x9E, 0x8D, 0x32, 0x88, 0x26, 0x1A, 0x3F, 0x61, 0xE8, 0x55, 0x2D, 0x16};
+const unsigned int DSTAR_DATA_SYNC_LENGTH_BYTES   = 3U;
+const unsigned int DSTAR_DATA_SYNC_LENGTH_SYMBOLS = DSTAR_DATA_SYNC_LENGTH_BYTES * 8U;
+const unsigned int DSTAR_DATA_SYNC_LENGTH_SAMPLES = DSTAR_DATA_SYNC_LENGTH_SYMBOLS * DSTAR_RADIO_SYMBOL_LENGTH;
 
-const uint8_t      DSTAR_SLOW_DATA_TYPE_TEXT   = 0x40U;
-const uint8_t      DSTAR_SLOW_DATA_TYPE_HEADER = 0x50U;
+const uint8_t DSTAR_DATA_SYNC_BYTES[] = {0x9E, 0x8D, 0x32, 0x88, 0x26, 0x1A, 0x3F, 0x61, 0xE8, 0x55, 0x2D, 0x16};
 
-const uint8_t      DSTAR_SCRAMBLER_BYTES[] = {0x70U, 0x4FU, 0x93U};
+// D-Star bit order version of 0x55 0x6E 0x0A
+const uint32_t DSTAR_FRAME_SYNC_DATA = 0x00557650U;
+const uint32_t DSTAR_FRAME_SYNC_MASK = 0x00FFFFFFU;
+const bool     DSTAR_FRAME_SYNC_SYMBOLS[] = {false, true, false, true, false, true, false, true, false, true, true, true, false, true, true, false, false, true, false, true, false, false, false, false};
+
+// D-Star bit order version of 0x55 0x2D 0x16
+const uint32_t DSTAR_DATA_SYNC_DATA = 0x00AAB468U;
+const uint32_t DSTAR_DATA_SYNC_MASK = 0x00FFFFFFU;
+const bool     DSTAR_DATA_SYNC_SYMBOLS[] = {true, false, true, false, true, false, true, false, true, false, true, true, false, true, false, false, false, true, true, false, true, false, false, false};
+
+// D-Star bit order version of 0x55 0x55 0xC8 0x7A
+const uint32_t DSTAR_END_SYNC_DATA = 0xAAAA135EU;
+const uint32_t DSTAR_END_SYNC_MASK = 0xFFFFFFFFU;
+const uint8_t  DSTAR_END_SYNC_BYTES[] = {0x55, 0x55, 0x55, 0x55, 0xC8, 0x7A, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+
+const uint8_t  DSTAR_SLOW_DATA_TYPE_TEXT   = 0x40U;
+const uint8_t  DSTAR_SLOW_DATA_TYPE_HEADER = 0x50U;
+
+const uint8_t  DSTAR_SCRAMBLER_BYTES[] = {0x70U, 0x4FU, 0x93U};
 
 #endif
 

DStarRX.cpp

@@ -22,18 +22,12 @@
 #include "DStarRX.h"
 #include "Utils.h"
 
-const unsigned int BUFFER_LENGTH = 200U;
-
-const uint32_t PLLMAX = 0x10000U;
-const uint32_t PLLINC = PLLMAX / DSTAR_RADIO_BIT_LENGTH;
-const uint32_t INC    = PLLINC / 32U;
-
-const unsigned int MAX_SYNC_BITS = 100U * DSTAR_DATA_LENGTH_BITS;
+const unsigned int MAX_FRAMES = 150U;
 
 // D-Star bit order version of 0x55 0x55 0x6E 0x0A
 const uint32_t FRAME_SYNC_DATA = 0x00557650U;
 const uint32_t FRAME_SYNC_MASK = 0x00FFFFFFU;
-const uint8_t  FRAME_SYNC_ERRS = 2U;
+const uint8_t  FRAME_SYNC_ERRS = 1U;
 
 // D-Star bit order version of 0x55 0x2D 0x16
 const uint32_t DATA_SYNC_DATA = 0x00AAB468U;
@@ -237,14 +231,24 @@ const uint16_t CCITT_TABLE[] = {
   0xf78fU, 0xe606U, 0xd49dU, 0xc514U, 0xb1abU, 0xa022U, 0x92b9U, 0x8330U,
   0x7bc7U, 0x6a4eU, 0x58d5U, 0x495cU, 0x3de3U, 0x2c6aU, 0x1ef1U, 0x0f78U};
 
+const uint16_t NOENDPTR = 9999U;
+
 CDStarRX::CDStarRX() :
-m_pll(0U),
-m_prev(false),
 m_rxState(DSRXS_NONE),
-m_patternBuffer(0x00U),
-m_rxBuffer(),
-m_rxBufferBits(0U),
-m_dataBits(0U),
+m_bitBuffer(),
+m_headerBuffer(),
+m_dataBuffer(),
+m_bitPtr(0U),
+m_headerPtr(0U),
+m_dataPtr(0U),
+m_startPtr(NOENDPTR),
+m_syncPtr(NOENDPTR),
+m_minSyncPtr(NOENDPTR),
+m_maxSyncPtr(NOENDPTR),
+m_maxFrameCorr(0),
+m_maxDataCorr(0),
+m_frameCount(0U),
+m_countdown(0U),
 m_mar(0U),
 m_pathMetric(),
 m_pathMemory0(),
@@ -259,14 +263,20 @@ m_rssiCount(0U)
 
 void CDStarRX::reset()
 {
-  m_pll           = 0U;
-  m_prev          = false;
-  m_rxState       = DSRXS_NONE;
-  m_patternBuffer = 0x00U;
-  m_rxBufferBits  = 0U;
-  m_dataBits      = 0U;
-  m_rssiAccum     = 0U;
-  m_rssiCount     = 0U;
+  m_rxState      = DSRXS_NONE;
+  m_headerPtr    = 0U;
+  m_dataPtr      = 0U;
+  m_bitPtr       = 0U;
+  m_maxFrameCorr = 0;
+  m_maxDataCorr  = 0;
+  m_startPtr     = NOENDPTR;
+  m_syncPtr      = NOENDPTR;
+  m_minSyncPtr   = NOENDPTR;
+  m_maxSyncPtr   = NOENDPTR;
+  m_frameCount   = 0U;
+  m_countdown    = 0U;
+  m_rssiAccum    = 0U;
+  m_rssiCount    = 0U;
 }
 
 void CDStarRX::samples(const q15_t* samples, const uint16_t* rssi, uint8_t length)
@@ -275,125 +285,117 @@ void CDStarRX::samples(const q15_t* samples, const uint16_t* rssi, uint8_t lengt
     m_rssiAccum += rssi[i];
     m_rssiCount++;
 
-    bool bit = samples[i] < 0;
+    q15_t sample = samples[i];
 
-    if (bit != m_prev) {
-      if (m_pll < (PLLMAX / 2U))
-        m_pll += INC;
-      else
-        m_pll -= INC;
+    m_bitBuffer[m_bitPtr] <<= 1;
+    if (sample < 0)
+      m_bitBuffer[m_bitPtr] |= 0x01U;
+
+    m_dataBuffer[m_dataPtr] = sample;
+
+    switch (m_rxState) {
+      case DSRXS_HEADER:
+        processHeader(sample);
+        break;
+      case DSRXS_DATA:
+        processData();
+        break;
+      default:
+        processNone(sample);
+        break;
     }
 
-    m_prev = bit;
+    m_dataPtr++;
+    if (m_dataPtr >= DSTAR_DATA_LENGTH_SAMPLES)
+      m_dataPtr = 0U;
 
-    m_pll += PLLINC;
-
-    if (m_pll >= PLLMAX) {
-      m_pll -= PLLMAX;
-
-      switch (m_rxState) {
-        case DSRXS_NONE:
-          processNone(bit);
-          break;
-        case DSRXS_HEADER:
-          processHeader(bit);
-          break;
-        case DSRXS_DATA:
-          processData(bit);
-          break;
-        default:
-          break;
-      }
-    }
+    m_bitPtr++;
+    if (m_bitPtr >= DSTAR_RADIO_SYMBOL_LENGTH)
+      m_bitPtr = 0U;
   }
 }
 
-void CDStarRX::processNone(bool bit)
+void CDStarRX::processNone(q15_t sample)
 {
-  m_patternBuffer <<= 1;
-  if (bit)
-    m_patternBuffer |= 0x01U;
-
   // 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");
-
-    ::memset(m_rxBuffer, 0x00U, DSTAR_FEC_SECTION_LENGTH_BYTES);
-    m_rxBufferBits = 0U;
+  bool ret = correlateFrameSync();
+  if (ret) {
+    m_countdown = 5U;
+	
+    m_headerBuffer[m_headerPtr] = sample;
+    m_headerPtr++;
 
     m_rssiAccum = 0U;
     m_rssiCount = 0U;
 
     m_rxState = DSRXS_HEADER;
+
     return;
   }
 
-  // Exact matching of the data sync bit sequence
-  if (countBits32((m_patternBuffer & DATA_SYNC_MASK) ^ DATA_SYNC_DATA) == 0U) {
+  // Fuzzy matching of the data sync bit sequence
+  ret = correlateDataSync();
+  if (ret) {
     DEBUG1("DStarRX: found data sync in None");
 
     io.setDecode(true);
     io.setADCDetection(true);
 
-    // Suppress RSSI on the dummy sync message
-    m_rssiAccum = 0U;
-    m_rssiCount = 0U;
-
-    ::memcpy(m_rxBuffer, DSTAR_DATA_SYNC_BYTES, DSTAR_DATA_LENGTH_BYTES);
-    writeRSSIData(m_rxBuffer);
-
-    ::memset(m_rxBuffer, 0x00U, DSTAR_DATA_LENGTH_BYTES + 2U);
-    m_rxBufferBits = 0U;
-
-    m_dataBits  = MAX_SYNC_BITS;
-    m_rxState   = DSRXS_DATA;
-    return;
+    m_rxState = DSRXS_DATA;
   }
 }
 
-void CDStarRX::processHeader(bool bit)
+void CDStarRX::processHeader(q15_t sample)
 {
-  m_patternBuffer <<= 1;
-  if (bit)
-    m_patternBuffer |= 0x01U;
+  if (m_countdown > 0U) {
+    correlateFrameSync();
+    m_countdown--;
+  }
 
-  WRITE_BIT2(m_rxBuffer, m_rxBufferBits, bit);
-  m_rxBufferBits++;
+  m_headerBuffer[m_headerPtr] = sample;
+  m_headerPtr++;
 
   // A full FEC header
-  if (m_rxBufferBits == DSTAR_FEC_SECTION_LENGTH_BITS) {
-    // Process the scrambling, interleaving and FEC, then return if the chcksum was correct
-    unsigned char header[DSTAR_HEADER_LENGTH_BYTES];
-    bool ok = rxHeader(m_rxBuffer, header);
-    if (ok) {
+  if (m_headerPtr == (DSTAR_FEC_SECTION_LENGTH_SAMPLES + DSTAR_RADIO_SYMBOL_LENGTH)) {
+    uint8_t buffer[DSTAR_FEC_SECTION_LENGTH_BYTES];
+    samplesToBits(m_headerBuffer, DSTAR_RADIO_SYMBOL_LENGTH, DSTAR_FEC_SECTION_LENGTH_SYMBOLS, buffer, DSTAR_FEC_SECTION_LENGTH_SAMPLES);
+
+    // Process the scrambling, interleaving and FEC, then return true if the chcksum was correct
+    uint8_t header[DSTAR_HEADER_LENGTH_BYTES];
+    bool ok = rxHeader(buffer, header);
+    if (!ok) {
+      // The checksum failed, return to looking for syncs
+      m_rxState = DSRXS_NONE;
+      m_maxFrameCorr = 0;
+      m_maxDataCorr  = 0;
+    } else {
       io.setDecode(true);
       io.setADCDetection(true);
 
       writeRSSIHeader(header);
-
-      ::memset(m_rxBuffer, 0x00U, DSTAR_DATA_LENGTH_BYTES + 2U);
-      m_rxBufferBits = 0U;
-
-      m_rxState  = DSRXS_DATA;
-      m_dataBits = MAX_SYNC_BITS;
-    } else {
-      // The checksum failed, return to looking for syncs
-      m_rxState = DSRXS_NONE;
     }
   }
+
+  // Ready to start the first data section
+  if (m_headerPtr == (DSTAR_FEC_SECTION_LENGTH_SAMPLES + 2U * DSTAR_RADIO_SYMBOL_LENGTH)) {
+    m_frameCount = 0U;
+    m_dataPtr    = 0U;
+
+    m_startPtr   = 476U;
+    m_syncPtr    = 471U;
+    m_maxSyncPtr = 472U;
+    m_minSyncPtr = 470U;
+
+    DEBUG5("DStarRX: calc start/sync/max/min", m_startPtr, m_syncPtr, m_maxSyncPtr, m_minSyncPtr);
+
+    m_rxState = DSRXS_DATA;
+  }
 }
 
-void CDStarRX::processData(bool bit)
+void CDStarRX::processData()
 {
-  m_patternBuffer <<= 1;
-  if (bit)
-    m_patternBuffer |= 0x01U;
-
-  WRITE_BIT2(m_rxBuffer, m_rxBufferBits, bit);
-  m_rxBufferBits++;
-
   // Fuzzy matching of the end frame sequences
-  if (countBits32((m_patternBuffer & END_SYNC_MASK) ^ END_SYNC_DATA) <= END_SYNC_ERRS) {
+  if (countBits32((m_bitBuffer[m_bitPtr] & DSTAR_END_SYNC_MASK) ^ DSTAR_END_SYNC_DATA) <= END_SYNC_ERRS) {
     DEBUG1("DStarRX: Found end sync in Data");
 
     io.setDecode(false);
@@ -401,35 +403,24 @@ void CDStarRX::processData(bool bit)
 
     serial.writeDStarEOT();
 
+    m_maxFrameCorr = 0;
+    m_maxDataCorr  = 0;
+
     m_rxState = DSRXS_NONE;
     return;
   }
 
   // Fuzzy matching of the data sync bit sequence
-  bool syncSeen = false;
-  if (m_rxBufferBits >= (DSTAR_DATA_LENGTH_BITS - 3U)) {
-    if (countBits32((m_patternBuffer & DATA_SYNC_MASK) ^ DATA_SYNC_DATA) <= DATA_SYNC_ERRS) {
-      m_rxBufferBits = DSTAR_DATA_LENGTH_BITS;
-      m_dataBits     = MAX_SYNC_BITS;
-      syncSeen       = true;
-    }
+  if (m_minSyncPtr < m_maxSyncPtr) {
+    if (m_dataPtr >= m_minSyncPtr && m_dataPtr <= m_maxSyncPtr)
+      correlateDataSync();
+  } else {
+    if (m_dataPtr >= m_minSyncPtr || m_dataPtr <= m_maxSyncPtr)
+      correlateDataSync();
   }
 
-  // Check to see if the sync is arriving late
-  if (m_rxBufferBits == DSTAR_DATA_LENGTH_BITS && !syncSeen) {
-    for (uint8_t i = 1U; i <= 3U; i++) {
-      uint32_t syncMask = DATA_SYNC_MASK >> i;
-      uint32_t syncData = DATA_SYNC_DATA >> i;
-      if (countBits32((m_patternBuffer & syncMask) ^ syncData) <= DATA_SYNC_ERRS) {
-        m_rxBufferBits -= i;
-        break;
-      }
-    }
-  }
-
-  m_dataBits--;
-
-  if (m_dataBits == 0U) {
+  // We've not seen a data sync for too long, signal RXLOST and change to RX_NONE
+  if (m_frameCount >= MAX_FRAMES) {
     DEBUG1("DStarRX: data sync timed out, lost lock");
 
     io.setDecode(false);
@@ -437,24 +428,35 @@ void CDStarRX::processData(bool bit)
 
     serial.writeDStarLost();
 
+    m_maxFrameCorr = 0;
+    m_maxDataCorr  = 0;
+
     m_rxState = DSRXS_NONE;
     return;
   }
 
-  // Send a data frame to the host if the required number of bits have been received, or if a data sync has been seen
-  if (m_rxBufferBits == DSTAR_DATA_LENGTH_BITS) {
-    if (syncSeen) {
-      m_rxBuffer[9U]  = DSTAR_DATA_SYNC_BYTES[9U];
-      m_rxBuffer[10U] = DSTAR_DATA_SYNC_BYTES[10U];
-      m_rxBuffer[11U] = DSTAR_DATA_SYNC_BYTES[11U];
-	    writeRSSIData(m_rxBuffer);
-    } else {
-	    serial.writeDStarData(m_rxBuffer, DSTAR_DATA_LENGTH_BYTES);
-	  }
+  // Send a data frame to the host if the required number of bits have been received
+  if (m_dataPtr == m_maxSyncPtr) {
+    uint8_t buffer[DSTAR_DATA_LENGTH_BYTES + 2U];
+    samplesToBits(m_dataBuffer, m_startPtr, DSTAR_DATA_LENGTH_SYMBOLS, buffer, DSTAR_DATA_LENGTH_SAMPLES);
 
-    // Start the next frame
-    ::memset(m_rxBuffer, 0x00U, DSTAR_DATA_LENGTH_BYTES + 2U);
-    m_rxBufferBits = 0U;
+    if ((m_frameCount % 21U) == 0U) {
+      if (m_frameCount == 0U) {
+        buffer[9U]  = DSTAR_DATA_SYNC_BYTES[9U];
+        buffer[10U] = DSTAR_DATA_SYNC_BYTES[10U];
+        buffer[11U] = DSTAR_DATA_SYNC_BYTES[11U];
+        DEBUG5("DStarRX: found start/sync/max/min", m_startPtr, m_syncPtr, m_maxSyncPtr, m_minSyncPtr);
+      }
+
+      writeRSSIData(buffer);
+    } else {
+      serial.writeDStarData(buffer, DSTAR_DATA_LENGTH_BYTES);
+    }
+
+    m_frameCount++;
+
+    m_maxFrameCorr = 0;
+    m_maxDataCorr  = 0;
   }
 }
 
@@ -500,6 +502,105 @@ void CDStarRX::writeRSSIData(unsigned char* data)
   m_rssiCount = 0U;
 }
 
+bool CDStarRX::correlateFrameSync()
+{
+  if (countBits32((m_bitBuffer[m_bitPtr] & DSTAR_FRAME_SYNC_MASK) ^ DSTAR_FRAME_SYNC_DATA) <= FRAME_SYNC_ERRS) {
+    uint16_t ptr = m_dataPtr + DSTAR_DATA_LENGTH_SAMPLES - DSTAR_FRAME_SYNC_LENGTH_SAMPLES + DSTAR_RADIO_SYMBOL_LENGTH;
+    if (ptr >= DSTAR_DATA_LENGTH_SAMPLES)
+      ptr -= DSTAR_DATA_LENGTH_SAMPLES;
+
+    q31_t corr = 0;
+
+    for (uint8_t i = 0U; i < DSTAR_FRAME_SYNC_LENGTH_SYMBOLS; i++) {
+      q15_t val = m_dataBuffer[ptr];
+
+      if (DSTAR_FRAME_SYNC_SYMBOLS[i])
+        corr -= val;
+      else
+        corr += val;
+
+      ptr += DSTAR_RADIO_SYMBOL_LENGTH;
+      if (ptr >= DSTAR_DATA_LENGTH_SAMPLES)
+        ptr -= DSTAR_DATA_LENGTH_SAMPLES;
+    }
+
+    if (corr > m_maxFrameCorr) {
+      m_maxFrameCorr = corr;
+      m_headerPtr    = 0U;
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool CDStarRX::correlateDataSync()
+{
+  uint8_t maxErrs = 0U;
+  if (m_rxState == DSRXS_DATA)
+    maxErrs = DATA_SYNC_ERRS;
+
+  if (countBits32((m_bitBuffer[m_bitPtr] & DSTAR_DATA_SYNC_MASK) ^ DSTAR_DATA_SYNC_DATA) <= maxErrs) {
+    uint16_t ptr = m_dataPtr + DSTAR_DATA_LENGTH_SAMPLES - DSTAR_DATA_SYNC_LENGTH_SAMPLES + DSTAR_RADIO_SYMBOL_LENGTH;
+    if (ptr >= DSTAR_DATA_LENGTH_SAMPLES)
+      ptr -= DSTAR_DATA_LENGTH_SAMPLES;
+
+    q31_t corr = 0;
+
+    for (uint8_t i = 0U; i < DSTAR_DATA_SYNC_LENGTH_SYMBOLS; i++) {
+      q15_t val = m_dataBuffer[ptr];
+
+      if (DSTAR_DATA_SYNC_SYMBOLS[i])
+        corr -= val;
+      else
+        corr += val;
+
+      ptr += DSTAR_RADIO_SYMBOL_LENGTH;
+      if (ptr >= DSTAR_DATA_LENGTH_SAMPLES)
+        ptr -= DSTAR_DATA_LENGTH_SAMPLES;
+    }
+
+    if (corr > m_maxDataCorr) {
+      m_maxDataCorr = corr;
+      m_frameCount  = 0U;
+
+      m_syncPtr    = m_dataPtr;
+
+      m_startPtr   = m_dataPtr + DSTAR_RADIO_SYMBOL_LENGTH;
+      if (m_startPtr >= DSTAR_DATA_LENGTH_SAMPLES)
+        m_startPtr -= DSTAR_DATA_LENGTH_SAMPLES;
+
+      m_maxSyncPtr = m_syncPtr + 1U;
+      if (m_maxSyncPtr >= DSTAR_DATA_LENGTH_SAMPLES)
+        m_maxSyncPtr -= DSTAR_DATA_LENGTH_SAMPLES;
+
+      m_minSyncPtr = m_syncPtr + DSTAR_DATA_LENGTH_SAMPLES - 1U;
+      if (m_minSyncPtr >= DSTAR_DATA_LENGTH_SAMPLES)
+        m_minSyncPtr -= DSTAR_DATA_LENGTH_SAMPLES;
+
+      return true;
+    }
+  }
+
+  return false;
+}
+
+void CDStarRX::samplesToBits(const q15_t* inBuffer, uint16_t start, uint16_t count, uint8_t* outBuffer, uint16_t limit)
+{
+  for (uint16_t i = 0U; i < count; i++) {
+    q15_t sample = inBuffer[start];
+
+    if (sample < 0)
+      WRITE_BIT2(outBuffer, i, true);
+    else
+      WRITE_BIT2(outBuffer, i, false);
+
+    start += DSTAR_RADIO_SYMBOL_LENGTH;
+    if (start >= limit)
+      start -= limit;
+  }
+}
+
 bool CDStarRX::rxHeader(uint8_t* in, uint8_t* out)
 {
   int i;

DStarRX.h

@@ -37,13 +37,21 @@ public:
   void reset();
 
 private:
-  uint32_t     m_pll;
-  bool         m_prev;
   DSRX_STATE   m_rxState;
-  uint32_t     m_patternBuffer;
-  uint8_t      m_rxBuffer[100U];
-  unsigned int m_rxBufferBits;
-  unsigned int m_dataBits;
+  uint32_t     m_bitBuffer[DSTAR_RADIO_SYMBOL_LENGTH];
+  q15_t        m_headerBuffer[DSTAR_FEC_SECTION_LENGTH_SAMPLES + 2U * DSTAR_RADIO_SYMBOL_LENGTH];
+  q15_t        m_dataBuffer[DSTAR_DATA_LENGTH_SAMPLES];
+  uint16_t     m_bitPtr;
+  uint16_t     m_headerPtr;
+  uint16_t     m_dataPtr;
+  uint16_t     m_startPtr;
+  uint16_t     m_syncPtr;
+  uint16_t     m_minSyncPtr;
+  uint16_t     m_maxSyncPtr;
+  q31_t        m_maxFrameCorr;
+  q31_t        m_maxDataCorr;
+  uint16_t     m_frameCount;
+  uint8_t      m_countdown;
   unsigned int m_mar;
   int          m_pathMetric[4U];
   unsigned int m_pathMemory0[42U];
@@ -54,9 +62,12 @@ private:
   uint32_t     m_rssiAccum;
   uint16_t     m_rssiCount;
   
-  void    processNone(bool bit);
-  void    processHeader(bool bit);
-  void    processData(bool bit);
+  void    processNone(q15_t sample);
+  void    processHeader(q15_t sample);
+  void    processData();
+  bool    correlateFrameSync();
+  bool    correlateDataSync();
+  void    samplesToBits(const q15_t* inBuffer, uint16_t start, uint16_t count, uint8_t* outBuffer, uint16_t limit);
   void    writeRSSIHeader(unsigned char* header);
   void    writeRSSIData(unsigned char* data);
   bool    rxHeader(uint8_t* in, uint8_t* out);

DStarTX.cpp

@@ -198,7 +198,7 @@ m_txDelay(60U)       // 100ms
 {
   ::memset(m_modState, 0x00U, 20U * sizeof(q15_t));
 
-  m_modFilter.L           = DSTAR_RADIO_BIT_LENGTH;
+  m_modFilter.L           = DSTAR_RADIO_SYMBOL_LENGTH;
   m_modFilter.phaseLength = GAUSSIAN_0_35_FILTER_PHASE_LEN;
   m_modFilter.pCoeffs     = GAUSSIAN_0_35_FILTER;
   m_modFilter.pState      = m_modState;
@@ -252,8 +252,8 @@ void CDStarTX::process()
     m_buffer.get();
 
     for (uint8_t j = 0U; j < 3U; j++) {
-      for (uint8_t i = 0U; i < DSTAR_EOT_LENGTH_BYTES; i++)
-        m_poBuffer[m_poLen++] = DSTAR_EOT_BYTES[i];
+      for (uint8_t i = 0U; i < DSTAR_END_SYNC_LENGTH_BYTES; i++)
+        m_poBuffer[m_poLen++] = DSTAR_END_SYNC_BYTES[i];
     }
      
     m_poPtr = 0U;
@@ -262,11 +262,11 @@ void CDStarTX::process()
   if (m_poLen > 0U) {
     uint16_t space = io.getSpace();
     
-    while (space > (8U * DSTAR_RADIO_BIT_LENGTH)) {
+    while (space > (8U * DSTAR_RADIO_SYMBOL_LENGTH)) {
       uint8_t c = m_poBuffer[m_poPtr++];
       writeByte(c);
 
-      space -= 8U * DSTAR_RADIO_BIT_LENGTH;
+      space -= 8U * DSTAR_RADIO_SYMBOL_LENGTH;
       
       if (m_poPtr >= m_poLen) {
         m_poPtr = 0U;
@@ -412,7 +412,7 @@ void CDStarTX::txHeader(const uint8_t* in, uint8_t* out) const
 void CDStarTX::writeByte(uint8_t c)
 {
   q15_t inBuffer[8U];
-  q15_t outBuffer[DSTAR_RADIO_BIT_LENGTH * 8U];
+  q15_t outBuffer[DSTAR_RADIO_SYMBOL_LENGTH * 8U];
 
   uint8_t mask = 0x01U;
 
@@ -427,7 +427,7 @@ void CDStarTX::writeByte(uint8_t c)
 
   ::arm_fir_interpolate_q15(&m_modFilter, inBuffer, outBuffer, 8U);
   
-  io.write(STATE_DSTAR, outBuffer, DSTAR_RADIO_BIT_LENGTH * 8U);
+  io.write(STATE_DSTAR, outBuffer, DSTAR_RADIO_SYMBOL_LENGTH * 8U);
 }
 
 void CDStarTX::setTXDelay(uint8_t delay)

SerialPort.cpp

@@ -592,8 +592,7 @@ void CSerialPort::process()
         m_buffer[0U] = c;
         m_ptr = 1U;
         m_len = 0U;
-      }
-      else {
+      } else {
         m_ptr = 0U;
         m_len = 0U;
       }