Add more frame processing.

AX25Demodulator.cpp

@@ -20,22 +20,102 @@
 #include "Globals.h"
 #include "AX25Demodulator.h"
 
-const float DELAY       = 0.000448F;
+const float32_t DELAY       = 0.000448F;
-const float SAMPLE_RATE = 24000.0F;
+const float32_t SAMPLE_RATE = 24000.0F;
+const float32_t SYMBOL_RATE = 1200.0F;
 
 const uint16_t DELAY_LEN = uint16_t((DELAY / (1.0F / SAMPLE_RATE)) + 0.5F);
 
-CAX25Demodulator::CAX25Demodulator() :
+const float32_t SAMPLES_PER_SYMBOL = SAMPLE_RATE / SYMBOL_RATE;
+const float32_t PLL_LIMIT          = SAMPLES_PER_SYMBOL / 2.0F;
+
+// XXX This is for the wrong sample rate
+const uint32_t LPF_FILTER_LEN = 96;
+
+q15_t lpfCoeffs[] = {
+    0,     1,     3,     5,     8,    11,    14,    17,    19,    20,    18,    14,
+    7,    -2,   -16,   -33,   -53,   -76,  -101,  -126,  -151,  -174,  -194,  -208,
+ -215,  -212,  -199,  -173,  -133,   -79,   -10,    74,   173,   287,   413,   549,
+  693,   842,   993,  1142,  1287,  1423,  1547,  1656,  1747,  1817,  1865,  1889,
+ 1889,  1865,  1817,  1747,  1656,  1547,  1423,  1287,  1142,   993,   842,   693,
+  549,   413,   287,   173,    74,   -10,   -79,  -133,  -173,  -199,  -212,  -215,
+ -208,  -194,  -174,  -151,  -126,  -101,   -76,   -53,   -33,   -16,    -2,     7,
+   14,    18,    20,    19,    17,    14,    11,     8,     5,     3,     1,     0,
+};
+
+// 64 Hz loop filter.
+// scipy.signal:
+//      loop_coeffs = firwin(9, [64.0/(1200/2)], width = None,
+//          pass_zero = True, scale = True, window='hann')
+//
+float32_t pllLoopCoeffs[] = {3.196252e-02F, 1.204223e-01F, 2.176819e-01F, 2.598666e-01F, 2.176819e-01F, 1.204223e-01F, 3.196252e-02F};
+
+CAX25Demodulator::CAX25Demodulator(float32_t* coeffs, uint16_t length) :
+m_audioFilter(),
+m_audioState(),
+m_lpfFilter(),
+m_lpfState(),
 m_delayLine(NULL),
 m_delayPos(0U),
-m_nrziState(false)
+m_nrziState(false),
+m_pllFilter(),
+m_pllState(),
+m_pllLast(false),
+m_pllBits(1U),
+m_pllCount(0.0F)
 {
   m_delayLine = new bool[2U * DELAY_LEN];
+
+  m_audioFilter.numTaps = length;
+  m_audioFilter.pState  = m_audioState;
+  m_audioFilter.pCoeffs = coeffs;
+
+  m_lpfFilter.numTaps = LPF_FILTER_LEN;
+  m_lpfFilter.pState  = m_lpfState;
+  m_lpfFilter.pCoeffs = lpfCoeffs;
+
+  m_pllFilter.numTaps = 7U;
+  m_pllFilter.pState  = m_pllState;
+  m_pllFilter.pCoeffs = pllLoopCoeffs;
 }
 
 bool CAX25Demodulator::process(const q15_t* samples, uint8_t length, CAX25Frame& frame)
 {
-  return false;
+  bool result = false;
+
+  float32_t input[RX_BLOCK_SIZE];
+  for (size_t i = 0; i < length; i++)
+    input[i] = float(samples[i]);
+
+  float32_t fa[RX_BLOCK_SIZE];
+  ::arm_fir_f32(&m_audioFilter, input, fa, RX_BLOCK_SIZE);
+
+  int16_t buffer[RX_BLOCK_SIZE];
+  for (uint8_t i = 0; i < length; i++) {
+      int16_t sample = int16_t(fa[i]);
+      bool     level = (sample >= 0);
+      bool   delayed = delay(level);
+      buffer[i] = (int16_t(level ^ delayed) << 1) - 1;
+  }
+
+  q15_t fc[RX_BLOCK_SIZE];
+  ::arm_fir_fast_q15(&m_lpfFilter, buffer, fc, RX_BLOCK_SIZE);
+
+  for (uint8_t i = 0; i < length; i++) {
+    bool bit = fc[i] >= 0;
+    bool sample = PLL(bit);
+
+    if (sample) {
+      // We will only ever get one frame because there are
+      // not enough bits in a block for more than one.
+      if (result)
+        hdlc_decoder_(NRZI(bit), true);
+      else
+        result = hdlc_decoder_(NRZI(bit), true);
+    }
+  }
+
+  return result;
 }
 
 bool CAX25Demodulator::delay(bool b)
@@ -59,3 +139,33 @@ bool CAX25Demodulator::NRZI(bool b)
   return result;
 }
 
+bool CAX25Demodulator::PLL(bool input)
+{
+  bool sample = false;
+		
+  if (input != m_pllLast or m_pllBits > 16U) {
+    // Record transition.
+    m_pllLast = input;
+
+    if (m_pllCount > PLL_LIMIT)
+      m_pllCount -= SAMPLES_PER_SYMBOL;
+
+    float32_t offset = m_pllCount / float32_t(m_pllBits);
+    float32_t jitter;
+    ::arm_fir_f32(&m_pllFilter, &offset, &jitter, 1U);
+
+    m_pllCount -= jitter / 2.0F;
+    m_pllBits = 1U;
+  } else {
+    if (m_pllCount > PLL_LIMIT) {
+      sample = true;
+      m_pllCount -= SAMPLES_PER_SYMBOL;
+      m_pllBits++;
+    }
+  }
+
+  m_pllCount += 1.0F;
+
+  return sample;
+}
+

AX25Demodulator.h

@@ -26,17 +26,27 @@
 
 class CAX25Demodulator {
 public:
-  CAX25Demodulator();
+  CAX25Demodulator(float32_t* coeffs, uint16_t length);
 
   bool process(const q15_t* samples, uint8_t length, CAX25Frame& frame);
 
 private:
-  bool*    m_delayLine;
+  arm_fir_instance_f32 m_audioFilter;
-  uint16_t m_delayPos;
+  float32_t            m_audioState[20U];
-  bool     m_nrziState;
+  arm_fir_instance_q15 m_lpfFilter;
+  q15_t                m_lpfState[120U];    // NoTaps + BlockSize - 1, 96 + 20 - 1 plus some spare
+  bool*                m_delayLine;
+  uint16_t             m_delayPos;
+  bool                 m_nrziState;
+  arm_fir_instance_f32 m_pllFilter;
+  float32_t            m_pllState[7U];
+  bool                 m_pllLast;
+  uint8_t              m_pllBits;
+  float32_t            m_pllCount;
 
   bool delay(bool b);
   bool NRZI(bool b);
+  bool PLL(bool b);
 };
 
 #endif