159 lines
5.0 KiB
C++
159 lines
5.0 KiB
C++
/* -*- c++ -*- */
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/*
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* gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
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*
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* Copyright (C) 2019, Libre Space Foundation <http://libre.space>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef INCLUDED_SATNOGS_IEEE802_15_4_VARIANT_DECODER_H
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#define INCLUDED_SATNOGS_IEEE802_15_4_VARIANT_DECODER_H
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#include <satnogs/api.h>
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#include <satnogs/decoder.h>
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#include <satnogs/whitening.h>
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#include <satnogs/crc.h>
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#include <satnogs/shift_reg.h>
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namespace gr {
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namespace satnogs {
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/*!
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* \brief A IEEE 802.15.4 like decoder
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*
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* The IEEE 802.15.4 uses the well known preamble + sync word synchronization
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* scheme. Many popular on Cubesats ICs like the Texas Instruments CC1xxx family
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* or the AXxxxx of On Semiconductors follow this scheme. This decoder
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* class provides a generic way to decode signals following this framing
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* scheme.
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*
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*/
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class SATNOGS_API ieee802_15_4_variant_decoder : public decoder {
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public:
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/**
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*
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* @param preamble the preamble should be a repeated word. Note that due to AGC
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* settling, the receiver may not receive the whole preamble. If the preamble
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* is indeed a repeated pattern, a portion of it can be given as parameter.
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* The block should be able to deal with this. However, a quite small subset
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* may lead to a larger number of false alarms
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*
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* @param preamble_threshold the maximum number of bits that are
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* allowed to be wrong at the preamble
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*
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* @param sync the synchronization work following the preamble
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*
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* @param sync_threshold the maximum number of bits that are
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* allowed to be wrong at the synchronization word
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*
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* @param crc the CRC scheme to use
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*
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* @param descrambler if set, data will be first descrambled by this descrambling
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* method
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*
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* @param var_len if set to true, variable length decoding is used. Otherwise,
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* the \p max_len parameter indicates the fixed frame size
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*
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* @param max_len the maximum allowed decode-able frame length
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*
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* @return shared pointer of the decoder
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*/
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static decoder::decoder_sptr
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make(const std::vector<uint8_t> &preamble,
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size_t preamble_threshold,
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const std::vector<uint8_t> &sync,
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size_t sync_threshold,
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crc::crc_t crc,
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whitening::whitening_sptr descrambler, bool var_len = true,
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size_t max_len = 1024);
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ieee802_15_4_variant_decoder(const std::vector<uint8_t> &preamble,
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size_t preamble_threshold,
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const std::vector<uint8_t> &sync,
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size_t sync_threshold,
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crc::crc_t crc,
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whitening::whitening_sptr descrambler,
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bool var_len = true,
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size_t max_len = 1024);
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~ieee802_15_4_variant_decoder();
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decoder_status_t
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decode(const void *in, int len);
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void
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reset();
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size_t
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input_multiple() const;
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private:
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/**
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* Decoding FSM states
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*/
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typedef enum {
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SEARCHING, //!< when searching for the start of the preamble
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SEARCHING_SYNC, //!< We have preamble, search for sync
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DECODING_GENERIC_FRAME_LEN, //!< Decoding the frame length
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DECODING_PAYLOAD //!< Decoding the payload
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} decoding_state_t;
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shift_reg d_preamble;
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shift_reg d_preamble_shift_reg;
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const size_t d_preamble_len;
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const size_t d_preamble_thrsh;
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shift_reg d_sync;
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shift_reg d_sync_shift_reg;
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const size_t d_sync_len;
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const size_t d_sync_thrsh;
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crc::crc_t d_crc;
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whitening::whitening_sptr d_descrambler;
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const bool d_var_len;
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size_t d_len;
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size_t d_length_field_len;
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decoding_state_t d_state;
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size_t d_cnt;
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uint8_t *d_pdu;
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decoder_status_t
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decode_var_len(const void *in, int len);
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decoder_status_t
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decode_const_len(const void *in, int len);
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int
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search_preamble(const uint8_t *in, int len);
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int
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search_sync(const uint8_t *in, int len);
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int
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decode_frame_len(const uint8_t *in);
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void
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decode_payload(decoder_status_t &status, const uint8_t *in, int len);
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bool
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check_crc();
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};
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} // namespace satnogs
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} // namespace gr
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#endif /* INCLUDED_SATNOGS_IEEE802_15_4_VARIANT_DECODER_H */
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