SyncDeframer.h

//
// Copyright 2018, Jeremy Cooper
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
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//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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#ifndef RDAT_SYNC_DEFRAMER_H
#define RDAT_SYNC_DEFRAMER_H

#include <stdint.h>
#include <stddef.h>
#include "SymbolDecoder.h"
#include "DATWordReceiver.h"

//
// Deframer which synchronizes on the R-DAT 0100010001 synchronization
// pattern and outputs ten-bit words.
//
class SyncDeframer : public SymbolDecoder
{
public:
  SyncDeframer(DATWordReceiver *receiver);
  virtual ~SyncDeframer();
  
  //
  // Reset the deframer. Dumps any accumulated bits and reverts to sync search
  // state.
  //
  void Reset();
  
  //
  // Called by lower-level bit slicer. Notifies decoder that the carrier/clock
  // PLL state has changed.  When carrier is dropped, the deframer resets
  // itself.
  //
  void ClockDetected(bool detected);
  
  //
  // Called by lower-level bit slicer when it decodes a bit. This in turn may
  // cause a word to be delivered to the downstream receiver.
  //
  void ReceiveBit(bool bit);

  //
  // Is there sufficient evidence that a preamble sequence is being received
  // right now?
  //
  bool PreambleDetected(void) const;
  
  //
  // Called by lower-level to indicate that an R-DAT track has started or
  // completed.
  //
  void TrackDetected(bool start);

  //
  // Called by lower-level to indicate that no more input is available.
  //
  void Stop();
  
protected:
  //
  // Have we been notified that we're inside a track at the moment?
  //
  bool mTrackDetected;
  
  //
  // 10-bit accumulating shift register.
  //
  int mFrame;

  //
  // Number of bits received since last sync position.
  //
  size_t mSyncBitCount;
  
  //
  // Current state.
  //
  enum { STATE_SYNC_SEARCH, STATE_SYNCED } mState;
  
  //
  // Consecutive pre-amble symbols detected.
  //
  size_t mPreambleSymbolCount;

  //
  // Current state of the preamble symbol check.
  //
  size_t mPreambleCheck;
  
  //
  // Recipient of our received words.
  //
  DATWordReceiver *mReceiver;
};

#endif