Merge pull request #362 from n0mjs710/link-audio-fidelity

FM link-mode network audio: anti-alias/reconstruction filtering

DMRTX.cpp

@@ -2,6 +2,7 @@
  *   Copyright (C) 2009-2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
  *   Copyright (C) 2017 by Andy Uribe CA6JAU
+ *   Copyright (C) 2022,2023,2026 by Adrian Musceac YO8RZZ
  *
  *   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
@@ -42,6 +43,12 @@ const uint8_t IDLE_DATA[] =
          0x36U, 0x00U, 0x0DU, 0xFFU, 0x57U, 0xD7U, 0x5DU, 0xF5U, 0xD0U, 0x03U, 0xF6U,
          0xE4U, 0x65U, 0x17U, 0x1BU, 0x48U, 0xCAU, 0x6DU, 0x4FU, 0xC6U, 0x10U, 0xB4U};
 
+// DT Terminator with LC, empty
+const uint8_t TERMINATOR_DATA[] =
+        {0x00U, 0xCCU, 0x01U, 0x80U, 0x01U, 0x94U, 0x01U, 0x48U, 0x08U, 0xB0U, 0x08U,
+         0x80U, 0x04U, 0xADU, 0xFFU, 0x57U, 0xD7U, 0x5DU, 0xF5U, 0xD9U, 0x65U, 0x90U,
+         0x01U, 0x78U, 0x00U, 0xD0U, 0x08U, 0x40U, 0x14U, 0x00U, 0x0DU, 0x80U, 0x15U};
+
 const uint8_t CACH_INTERLEAVE[] =
         { 1U,  2U,  3U,  5U,  6U,  7U,  9U, 10U, 11U, 13U, 15U, 16U, 17U, 19U, 20U, 21U, 23U,
          25U, 26U, 27U, 29U, 30U, 31U, 33U, 34U, 35U, 37U, 39U, 40U, 41U, 43U, 44U, 45U, 47U,
@@ -65,6 +72,7 @@ m_modFilter(),
 m_modState(),
 m_state(DMRTXSTATE_IDLE),
 m_idle(),
+m_aloha(),
 m_cachPtr(0U),
 m_shortLC(),
 m_newShortLC(),
@@ -74,7 +82,10 @@ m_poLen(0U),
 m_poPtr(0U),
 m_frameCount(0U),
 m_abortCount(),
-m_abort()
+m_abort(),
+m_controlChannel(false),
+m_trunking(false),
+m_colorCode(0U)
 {
   ::memset(m_modState, 0x00U, 16U * sizeof(q15_t));
 
@@ -211,6 +222,23 @@ uint8_t CDMRTX::writeShortLC(const uint8_t* data, uint16_t length)
   return 0U;
 }
 
+uint8_t CDMRTX::writeAloha(const uint8_t* data, uint16_t length)
+{
+  if (length != DMR_FRAME_LENGTH_BYTES)
+    return 4U;
+
+  ::memcpy(m_aloha, data, length);
+
+  // Stamp the slot type with the current colour code so that the result
+  // doesn't depend on the ordering of the ALOHA and SET_CONFIG commands.
+  CDMRSlotType slotType;
+  slotType.encode(m_colorCode, DT_CSBK, m_aloha);
+
+  m_controlChannel = true;
+
+  return 0U;
+}
+
 uint8_t CDMRTX::writeAbort(const uint8_t* data, uint16_t length)
 {
   if (length != 1U)
@@ -294,7 +322,7 @@ uint8_t CDMRTX::getSpace2() const
 
 void CDMRTX::createData(uint8_t slotIndex)
 {
-  if (m_fifo[slotIndex].getData() >= DMR_FRAME_LENGTH_BYTES && m_frameCount >= STARTUP_COUNT && m_abortCount[slotIndex] >= ABORT_COUNT) {
+  if ((m_fifo[slotIndex].getData() >= DMR_FRAME_LENGTH_BYTES) && (m_frameCount >= STARTUP_COUNT) && (m_abortCount[slotIndex] >= ABORT_COUNT)) {
     for (unsigned int i = 0U; i < DMR_FRAME_LENGTH_BYTES; i++) {
       m_fifo[slotIndex].get(m_poBuffer[i]);
       m_markBuffer[i] = MARK_NONE;
@@ -303,7 +331,11 @@ void CDMRTX::createData(uint8_t slotIndex)
     m_abort[slotIndex] = false;
     // Transmit an idle message
     for (unsigned int i = 0U; i < DMR_FRAME_LENGTH_BYTES; i++) {
-      m_poBuffer[i]   = m_idle[i];
+      if ((slotIndex == 0U) && m_controlChannel && m_trunking)
+        m_poBuffer[i] = m_aloha[i];
+      else
+        m_poBuffer[i] = m_idle[i];
+
       m_markBuffer[i] = MARK_NONE;
     }
   }
@@ -354,10 +386,14 @@ void CDMRTX::createCACH(uint8_t txSlotIndex, uint8_t rxSlotIndex)
     m_cachPtr = 0U;
 
   if (m_cachPtr == 0U) {
-    if (m_fifo[0U].getData() == 0U && m_fifo[1U].getData() == 0U)
-      ::memcpy(m_shortLC, EMPTY_SHORT_LC, 12U);
-    else
+    if ((m_fifo[0U].getData() == 0U) && (m_fifo[1U].getData() == 0U)) {
+      if (m_trunking)
+        ::memcpy(m_shortLC, m_newShortLC, 12U);
+      else
+        ::memcpy(m_shortLC, EMPTY_SHORT_LC, 12U);
+    } else {
       ::memcpy(m_shortLC, m_newShortLC, 12U);
+    }
   }
 
   ::memcpy(m_poBuffer, m_shortLC + m_cachPtr, 3U);
@@ -367,8 +403,8 @@ void CDMRTX::createCACH(uint8_t txSlotIndex, uint8_t rxSlotIndex)
 
   bool at = false;
   if (m_frameCount >= STARTUP_COUNT)
-    at = m_fifo[rxSlotIndex].getData() > 0U;
-  bool tc = txSlotIndex == 1U;
+    at = (m_fifo[rxSlotIndex].getData() > 0U);
+  bool tc  = (txSlotIndex == 1U);
   bool ls0 = true;            // For 1 and 2
   bool ls1 = true;
 
@@ -397,10 +433,20 @@ void CDMRTX::createCACH(uint8_t txSlotIndex, uint8_t rxSlotIndex)
 
 void CDMRTX::setColorCode(uint8_t colorCode)
 {
-  ::memcpy(m_idle, IDLE_DATA, DMR_FRAME_LENGTH_BYTES);
+  m_colorCode = colorCode;
+
+  if (m_trunking)
+    ::memcpy(m_idle, TERMINATOR_DATA, DMR_FRAME_LENGTH_BYTES);
+  else
+    ::memcpy(m_idle, IDLE_DATA, DMR_FRAME_LENGTH_BYTES);
 
   CDMRSlotType slotType;
-  slotType.encode(colorCode, DT_IDLE, m_idle);
+  if (m_trunking) {
+    slotType.encode(colorCode, DT_TERMINATOR_WITH_LC, m_idle);
+    slotType.encode(colorCode, DT_CSBK, m_aloha);
+  } else {
+    slotType.encode(colorCode, DT_IDLE, m_idle);
+  }
 }
 
 void CDMRTX::resetFifo1()
@@ -418,5 +464,12 @@ uint32_t CDMRTX::getFrameCount()
   return m_frameCount;
 }
 
-#endif
+void CDMRTX::setTrunking(bool trunking)
+{
+  m_trunking = trunking;
 
+  if (!trunking)
+    m_controlChannel = false;
+}
+
+#endif

DMRTX.h

@@ -1,6 +1,7 @@
 /*
  *   Copyright (C) 2015,2016,2017,2020 by Jonathan Naylor G4KLX
  *   Copyright (C) 2016 by Colin Durbridge G4EML
+ *   Copyright (C) 2026 by Adrian Musceac YO8RZZ
  *
  *   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
@@ -45,10 +46,12 @@ public:
   uint8_t writeData2(const uint8_t* data, uint16_t length);
 
   uint8_t writeShortLC(const uint8_t* data, uint16_t length);
+  uint8_t writeAloha(const uint8_t* data, uint16_t length);
   uint8_t writeAbort(const uint8_t* data, uint16_t length);
 
   void setStart(bool start);
   void setCal(bool start);
+  void setTrunking(bool trunking);
 
   void process();
   
@@ -62,11 +65,12 @@ public:
   void setColorCode(uint8_t colorCode);
 
 private:
-  CRingBuffer<uint8_t>                        m_fifo[2U];
+  CRingBuffer<uint8_t>             m_fifo[2U];
   arm_fir_interpolate_instance_q15 m_modFilter;
   q15_t                            m_modState[16U];    // blockSize + phaseLength - 1, 4 + 9 - 1 plus some spare
   DMRTXSTATE                       m_state;
   uint8_t                          m_idle[DMR_FRAME_LENGTH_BYTES];
+  uint8_t                          m_aloha[DMR_FRAME_LENGTH_BYTES];
   uint8_t                          m_cachPtr;
   uint8_t                          m_shortLC[12U];
   uint8_t                          m_newShortLC[12U];
@@ -77,6 +81,9 @@ private:
   uint32_t                         m_frameCount;
   uint32_t                         m_abortCount[2U];
   bool                             m_abort[2U];
+  bool                             m_controlChannel;
+  bool                             m_trunking;
+  uint8_t                          m_colorCode;
 
   void createData(uint8_t slotIndex);
   void createCACH(uint8_t txSlotIndex, uint8_t rxSlotIndex);
@@ -87,4 +94,3 @@ private:
 #endif
 
 #endif
-

FM.cpp

@@ -27,7 +27,8 @@ const uint16_t FM_TX_BLOCK_SIZE = 100U;
 const uint16_t FM_SERIAL_BLOCK_SIZE = 80U;//this is the number of sample pairs to send over serial. One sample pair is 3bytes.
                                           //three times this value shall never exceed 252
 const uint16_t FM_SERIAL_BLOCK_SIZE_BYTES = FM_SERIAL_BLOCK_SIZE * 3U;
-
+const uint16_t FM_LINK_EXT_GAP_MS = 60U;// How long a link-mode external-audio underrun is tolerated before it is
+                                        // treated as a real end of transmission (see linkStateMachine()).
 const uint8_t FS_LISTENING         = 0U;
 const uint8_t FS_KERCHUNK_RF       = 1U;
 const uint8_t FS_RELAYING_RF       = 2U;
@@ -62,10 +63,17 @@ m_ackMinTimer(),
 m_ackDelayTimer(),
 m_hangTimer(),
 m_reverseTimer(),
+m_extGapTimer(),
 m_needReverse(false),
 m_filterStage1(  724,   1448,   724, 32768, -37895, 21352),//3rd order Cheby Filter 300 to 2700Hz, 0.2dB passband ripple, sampling rate 24kHz
 m_filterStage2(32768,      0,-32768, 32768, -50339, 19052),
 m_filterStage3(32768, -65536, 32768, 32768, -64075, 31460),
+m_dsFilterStage1(m_filterStage1),//same coefficients, separate state
+m_dsFilterStage2(m_filterStage2),
+m_dsFilterStage3(m_filterStage3),
+m_usFilterStage1(m_filterStage1),//same coefficients, separate state
+m_usFilterStage2(m_filterStage2),
+m_usFilterStage3(m_filterStage3),
 m_blanking(),
 m_accessMode(1U),
 m_linkMode(false),
@@ -85,6 +93,7 @@ m_rssiAccum(0U),
 m_rssiCount(0U)
 {
   m_reverseTimer.setTimeout(0U, 150U);
+  m_extGapTimer.setTimeout(0U, FM_LINK_EXT_GAP_MS);
 
   insertDelay(100U);
 }
@@ -119,6 +128,7 @@ void CFM::repeaterSamples(bool cos, q15_t* samples, const uint16_t* rssi, uint8_
 
     q15_t currentExtSample;
     bool inputExt = m_inputExtRB.getSample(currentExtSample);//always consume the external input data so it does not overflow
+    currentExtSample = m_usFilterStage3.filter(m_usFilterStage2.filter(m_usFilterStage1.filter(currentExtSample)));
     inputExt = inputExt && m_extEnabled;
 
     switch (m_accessMode) {
@@ -200,8 +210,10 @@ void CFM::repeaterSamples(bool cos, q15_t* samples, const uint16_t* rssi, uint8_
     if (m_duplex) {
       if (m_state == FS_RELAYING_RF || m_state == FS_KERCHUNK_RF || m_state == FS_RELAYING_EXT || m_state == FS_KERCHUNK_EXT) {
         currentSample = m_blanking.process(currentSample);
-        if (m_extEnabled && (m_state == FS_RELAYING_RF || m_state == FS_KERCHUNK_RF))
-          m_downSampler.addSample(currentSample);
+        if (m_extEnabled && (m_state == FS_RELAYING_RF || m_state == FS_KERCHUNK_RF)) {
+          q15_t dsSample = m_dsFilterStage3.filter(m_dsFilterStage2.filter(m_dsFilterStage1.filter(currentSample)));
+          m_downSampler.addSample(dsSample);
+        }
 
         currentSample *= currentBoost;
       } else {
@@ -211,9 +223,11 @@ void CFM::repeaterSamples(bool cos, q15_t* samples, const uint16_t* rssi, uint8_
         if (m_state == FS_RELAYING_EXT || m_state == FS_KERCHUNK_EXT) {
           currentSample *= currentBoost;
         } else {
-          if (m_extEnabled && (m_state == FS_RELAYING_RF || m_state == FS_KERCHUNK_RF))
-            m_downSampler.addSample(currentSample);
-          continue; 
+          if (m_extEnabled && (m_state == FS_RELAYING_RF || m_state == FS_KERCHUNK_RF)) {
+            q15_t dsSample = m_dsFilterStage3.filter(m_dsFilterStage2.filter(m_dsFilterStage1.filter(currentSample)));
+            m_downSampler.addSample(dsSample);
+          }
+          continue;
         }
     }
 
@@ -250,14 +264,17 @@ void CFM::linkSamples(bool cos, q15_t* samples, uint8_t length)
 
   uint8_t i = 0U;
   for (; i < length; i++) {
-    // ARMv7-M has hardware integer division 
     q15_t currentRFSample = q15_t((q31_t(samples[i]) << 8) / m_rxLevel);
 
     if (m_noiseSquelch)
       cos = m_squelch.process(currentRFSample);
 
-    q15_t currentExtSample;
+    // Zero-initialized: getSample() leaves this untouched on underrun, and
+    // with the ext-gap debounce below, m_extSignal can now stay true for a
+    // few samples past that point
+    q15_t currentExtSample = 0;
     bool inputExt = m_inputExtRB.getSample(currentExtSample);//always consume the external input data so it does not overflow
+    currentExtSample = m_usFilterStage3.filter(m_usFilterStage2.filter(m_usFilterStage1.filter(currentExtSample)));
     inputExt = inputExt && m_extEnabled;
 
     switch (m_accessMode) {
@@ -327,7 +344,8 @@ void CFM::linkSamples(bool cos, q15_t* samples, uint8_t length)
 
     if (m_rfSignal && m_extEnabled) {
       q15_t currentSample = m_blanking.process(currentRFSample);
-      m_downSampler.addSample(currentSample);
+      q15_t dsSample = m_dsFilterStage3.filter(m_dsFilterStage2.filter(m_dsFilterStage1.filter(currentSample)));
+      m_downSampler.addSample(dsSample);
     }
 
     if (!m_extSignal)
@@ -407,6 +425,12 @@ void CFM::reset()
   m_inputExtRB.reset();
 
   m_downSampler.reset();
+  m_dsFilterStage1.reset();
+  m_dsFilterStage2.reset();
+  m_dsFilterStage3.reset();
+  m_usFilterStage1.reset();
+  m_usFilterStage2.reset();
+  m_usFilterStage3.reset();
   m_squelch.reset();
   
   m_needReverse = false;
@@ -601,6 +625,7 @@ void CFM::clock(uint8_t length)
   m_ackDelayTimer.clock(length);
   m_hangTimer.clock(length);
   m_reverseTimer.clock(length);
+  m_extGapTimer.clock(length);
 }
 
 void CFM::listeningStateDuplex(bool validRFSignal, bool validExtSignal)
@@ -1231,6 +1256,12 @@ void CFM::linkStateMachine(bool validRFSignal, bool validExtSignal)
     m_extSignal = true;
   }
 
+  if (validExtSignal && m_extGapTimer.isRunning()) {
+    // Recovered before the gap timer committed to a real loss below --
+    // m_extSignal was never flipped, so there is nothing else to undo.
+    m_extGapTimer.stop();
+  }
+
   if (!validRFSignal && m_rfSignal) {
     io.setDecode(false);
     io.setADCDetection(false);
@@ -1248,14 +1279,28 @@ void CFM::linkStateMachine(bool validRFSignal, bool validExtSignal)
   }
 
   if (!validExtSignal && m_extSignal) {
-    if (!m_rfSignal) {
-      DEBUG1("State to LISTENING");
-      m_state = FS_LISTENING;
-      serial.writeFMStatus(m_state);
-    }
+    // A missed/late sample used to flip m_extSignal false right here, on
+    // the very first bad sample, with zero debounce -- that is what
+    // actually keys the transmitter off (IO::process() drops PTT the
+    // instant the downstream TX buffer runs dry, see IO.cpp). A gap well
+    // under FM_LINK_EXT_GAP_MS is less offensive than the PTT
+    // drop-and-rekey it triggers. Give it a short grace period
+    // mirroring the RELAYING_EXT/RELAYING_WAIT_EXT pattern the
+    // non-link duplex/simplex paths already use for exactly this
+    // situation (see relayingExtStateDuplex()/relayingExtWaitStateDuplex()).
+    if (!m_extGapTimer.isRunning()) {
+      m_extGapTimer.start();
+    } else if (m_extGapTimer.hasExpired()) {
+      if (!m_rfSignal) {
+        DEBUG1("State to LISTENING");
+        m_state = FS_LISTENING;
+        serial.writeFMStatus(m_state);
+      }
 
-    m_needReverse = true;
-    m_extSignal   = false;
+      m_needReverse = true;
+      m_extSignal   = false;
+      m_extGapTimer.stop();
+    }
   }
 }
 

FM.h

@@ -75,10 +75,17 @@ private:
   CFMTimer             m_ackDelayTimer;
   CFMTimer             m_hangTimer;
   CFMTimer             m_reverseTimer;
+  CFMTimer             m_extGapTimer;   // debounce for link-mode ext-audio underrun, see linkStateMachine()
   bool                 m_needReverse;
   CFMDirectFormI       m_filterStage1;
   CFMDirectFormI       m_filterStage2;
   CFMDirectFormI       m_filterStage3;
+  CFMDirectFormI       m_dsFilterStage1; // anti-alias filter for the downsampler, own state
+  CFMDirectFormI       m_dsFilterStage2;
+  CFMDirectFormI       m_dsFilterStage3;
+  CFMDirectFormI       m_usFilterStage1; // reconstruction filter for the upsampler, own state
+  CFMDirectFormI       m_usFilterStage2;
+  CFMDirectFormI       m_usFilterStage3;
   CFMBlanking          m_blanking;
   uint8_t              m_accessMode;
   bool                 m_linkMode;

FMDownSampler.cpp

@@ -34,6 +34,7 @@ m_sampleIndex(0U)
 
 void CFMDownSampler::addSample(q15_t sample)
 {
+  sample = __SSAT(sample, 12);//clamp before packing to 12 bits
   uint32_t usample = uint32_t(int32_t(sample) + 2048);
   //only take one of three samples
   switch(m_sampleIndex){
@@ -74,6 +75,8 @@ uint16_t CFMDownSampler::getData()
 void CFMDownSampler::reset()
 {
   m_sampleIndex = 0U;
+  m_samplePack  = 0U;
+  m_ringBuffer.reset();
 }
 
 #endif

FMNoiseSquelch.cpp

@@ -36,7 +36,8 @@ m_count(0U),
 m_q0(0),
 m_q1(0),
 m_state(false),
-m_validCount(0U)
+m_validCount(0U),
+m_invalidCount(0U)
 {
 
 }
@@ -127,6 +128,8 @@ void CFMNoiseSquelch::reset()
   m_q1 = 0;
   m_state = false;
   m_count = 0U;
+  m_validCount = 0U;
+  m_invalidCount = 0U;
 }
 
 #endif

IODue.cpp

@@ -110,7 +110,7 @@ void CIO::initInt()
 #if !defined(USE_ALTERNATE_POCSAG_LEDS)
   pinMode(PIN_POCSAG, OUTPUT);
 #endif
-#if !defined(USE_ALTERNATE_POCSAG_LEDS)
+#if !defined(USE_ALTERNATE_FM_LEDS)
   pinMode(PIN_FM,     OUTPUT);
 #endif
 #endif

STMUART.cpp

@@ -61,7 +61,7 @@ void CSTMUART::handleIRQ()
   if (USART_GetITStatus(m_usart, USART_IT_RXNE)) {
     if(!m_rxFifo.isFull())
       m_rxFifo.put((uint8_t) USART_ReceiveData(m_usart));
-    USART_ClearITPendingBit(USART1, USART_IT_RXNE);
+    USART_ClearITPendingBit(m_usart, USART_IT_RXNE);
   }
 
   if (USART_GetITStatus(m_usart, USART_IT_TXE)) {
@@ -82,8 +82,12 @@ void CSTMUART::flush()
   if(m_usart == NULL)
     return;
 
-   // wait until the TXE shows the shift register is empty
-   while (USART_GetITStatus(m_usart, USART_FLAG_TXE))
+   // wait until the TX FIFO has drained
+   while (!m_txFifo.isEmpty())
+      ;
+
+   // wait until the TC flag shows the shift register is empty
+   while (USART_GetFlagStatus(m_usart, USART_FLAG_TC) == RESET)
       ;
 }
 

SerialPort.cpp

@@ -45,6 +45,7 @@ const uint8_t MMDVM_DSTAR_DATA   = 0x11U;
 const uint8_t MMDVM_DSTAR_LOST   = 0x12U;
 const uint8_t MMDVM_DSTAR_EOT    = 0x13U;
 
+const uint8_t MMDVM_DMR_ALOHA    = 0x17U;
 const uint8_t MMDVM_DMR_DATA1    = 0x18U;
 const uint8_t MMDVM_DMR_LOST1    = 0x19U;
 const uint8_t MMDVM_DMR_DATA2    = 0x1AU;
@@ -466,6 +467,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
 #endif
 
 #if defined(MODE_DMR)
+  bool trunking = (data[25U] & 128U) == 128U;
   uint8_t colorCode = data[26U];
   if (colorCode > 15U)
     return 4U;
@@ -484,7 +486,7 @@ uint8_t CSerialPort::setConfig(const uint8_t* data, uint16_t length)
 #if defined(MODE_DMR)
   m_dmrEnable    = dmrEnable;
   dmrDMOTX.setTXDelay(txDelay);
-
+  dmrTX.setTrunking(trunking);
   dmrTX.setColorCode(colorCode);
   dmrRX.setColorCode(colorCode);
   dmrRX.setDelay(dmrDelay);
@@ -743,7 +745,7 @@ void CSerialPort::setMode(MMDVM_STATE modemState)
       DEBUG1("Mode set to FM 20Khz Calibrate");
       break;
     case STATE_FMCAL25K:
-      DEBUG1("Mode set to FM 10Khz Calibrate");
+      DEBUG1("Mode set to FM 25Khz Calibrate");
       break;
     case STATE_FMCAL30K:
       DEBUG1("Mode set to FM 30Khz Calibrate");
@@ -1123,6 +1125,15 @@ void CSerialPort::processMessage(uint8_t type, const uint8_t* buffer, uint16_t l
       }
       break;
 
+    case MMDVM_DMR_ALOHA:
+      if (m_dmrEnable)
+        err = dmrTX.writeAloha(buffer, length);
+      if (err != 0U) {
+        DEBUG2("Received invalid DMR ALOHA", err);
+        sendNAK(type, err);
+      }
+      break;
+
     case MMDVM_DMR_ABORT:
       if (m_dmrEnable)
         err = dmrTX.writeAbort(buffer, length);

Version.h

@@ -19,6 +19,6 @@
 #if !defined(VERSION_H)
 #define  VERSION_H
 
-#define VERSION "20260219"
+#define VERSION "20260424"
 
 #endif