ax100_mode5.h

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/* -*- c++ -*- */
/*
 *  gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
 *
 *  Copyright (C) 2019-2023, Libre Space Foundation <http://libre.space>
 *
 *  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
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  SPDX-License-Identifier: GNU General Public License v3.0 or later
 */
 
#ifndef INCLUDED_SATNOGS_AX100_MODE5_H
#define INCLUDED_SATNOGS_AX100_MODE5_H
 
#include <gnuradio/satnogs/api.h>
#include <gnuradio/satnogs/crc.h>
#include <gnuradio/satnogs/decoder.h>
#include <gnuradio/satnogs/shift_reg.h>
#include <gnuradio/satnogs/whitening.h>
 
namespace gr {
namespace satnogs {
 
/*!
 * \brief This decode implements the AX100 mode 5 scheme
 *
 */
class SATNOGS_API ax100_mode5 : public decoder
{
public:
    using sptr = std::shared_ptr<ax100_mode5>;
    static sptr make(const std::vector<uint8_t>& preamble,
                     size_t preamble_threshold,
                     const std::vector<uint8_t>& sync,
                     size_t sync_threshold);
 
    ax100_mode5(const std::vector<uint8_t>& preamble,
                size_t preamble_threshold,
                const std::vector<uint8_t>& sync,
                size_t sync_threshold);
    ~ax100_mode5();
 
    decoder_status_t decode(const void* in, int len);
 
    void reset();
 
    size_t input_multiple() const;
 
private:
    /**
     * Decoding FSM
     */
    typedef enum {
        SEARCHING,          //!< when searching for the start of the preamble
        SEARCHING_SYNC,     //!< We have preamble, search for sync
        DECODING_FRAME_LEN, //!< Decoding the frame length
        DECODING_PAYLOAD    //!< Decoding the payload
    } decoding_state_t;
 
    shift_reg d_preamble;
    shift_reg d_preamble_shift_reg;
    const size_t d_preamble_len;
    const size_t d_preamble_thrsh;
    shift_reg d_sync;
    shift_reg d_sync_shift_reg;
    const size_t d_sync_len;
    const size_t d_sync_thrsh;
    decoding_state_t d_state;
    size_t d_cnt;
    size_t d_len;
    uint64_t d_frame_start;
    size_t d_length_field_len;
    uint8_t* d_pdu;
 
    int search_preamble(const uint8_t* in, int len);
 
    int search_sync(const uint8_t* in, int len);
 
    int decode_frame_len(const uint8_t* in, int len);
 
    void decode_payload(decoder_status_t& status, const uint8_t* in, int len);
};
 
} // namespace satnogs
} // namespace gr
 
#endif /* INCLUDED_SATNOGS_AX100_MODE5_H */