Code complete, but untested.

AX25Demodulator.h

@@ -23,6 +23,11 @@
 
 #include "AX25Frame.h"
 
+enum AX25_STATE {
+  AX25_IDLE,
+  AX25_SYNC,
+  AX25_RECEIVE
+};
 
 class CAX25Demodulator {
 public:
@@ -31,6 +36,7 @@ public:
   bool process(const q15_t* samples, uint8_t length, CAX25Frame& frame);
 
 private:
+  CAX25Frame           m_frame;
   arm_fir_instance_f32 m_audioFilter;
   float32_t            m_audioState[20U];
   arm_fir_instance_q15 m_lpfFilter;
@@ -43,10 +49,16 @@ private:
   bool                 m_pllLast;
   uint8_t              m_pllBits;
   float32_t            m_pllCount;
+  uint16_t             m_hdlcOnes;
+  bool                 m_hdlcFlag;
+  uint16_t             m_hdlcBuffer;
+  uint16_t             m_hdlcBits;
+  AX25_STATE           m_hdlcState;
 
   bool delay(bool b);
   bool NRZI(bool b);
   bool PLL(bool b);
+  bool HDLC(bool b);
 };
 
 #endif