138 lines
4.7 KiB
C++
138 lines
4.7 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) 2018, Libre Space Foundation <http://librespacefoundation.org/>
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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_FRAME_ACQUISITION_H
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#define INCLUDED_SATNOGS_FRAME_ACQUISITION_H
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#include <satnogs/api.h>
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#include <satnogs/whitening.h>
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#include <gnuradio/sync_block.h>
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namespace gr {
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namespace satnogs {
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/*!
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* \brief A generic frame acquisition block
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*
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* A generic frame acquisition block trying to cover a variaty of different
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* framing schemes.
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*
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* The goal of this block is to provide a unified way to acquire the frame
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* from different satellites with different but closely related framing schemes.
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* To keep the logic inside the block simple, it assumes that the received
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* bit stream is ready for framing extraction. Any bit stream coding, like
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* NRZI, Manchester, etc should be done prior this block.
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*
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* Currently the supported are:
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* - TI framing, constant frame length
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* - TI framing, variable frame length
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* - TI like framing, variable frame length with a 12-bit frame legth field
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* coded with Golay (24, 12, 8) scheme.
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*
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* The block supports also an arbitrary descrambler (if provided) using the
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* satnogs::whitening claass.
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*
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* For the CRC calculation (if any) the currently supported schemes are:
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* - CRC16-CCITT
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* - Reversed CRC16-CCITT
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* - CRC16-IBM
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* - CRC32-CCITT
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*
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* \ingroup satnogs
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*
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*/
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class SATNOGS_API frame_acquisition : virtual public gr::sync_block {
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public:
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typedef boost::shared_ptr<frame_acquisition> sptr;
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/**
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* Different framing schemes variants
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*/
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typedef enum {
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GENERIC_CONSTANT_FRAME_LEN = 0,//!< TI CCXXX like, constant frame length
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GENERIC_VAR_FRAME_LEN, //!< TI CCXXX like, variable frame length
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GOLAY24_CODED_FRAME_LEN //!< TI CCXXX like, variable frame length, 12-bit frame legth field coded with Golay (24, 12, 8)
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} variant_t;
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typedef enum {
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CRC_NONE = 0,
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CRC16_CCITT,
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CRC16_CCITT_REVERSED,
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CRC16_IBM,
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CRC32
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} checksum_t;
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/**
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* A generic frame acquisition block trying to cover a variaty of different
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* framing schemes.
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*
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* The goal of this block is to provide a unified way to acquire the frame
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* from different satellites with different but closely related framing schemes.
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* To keep the logic inside the block simple, it assumes that the received
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* bit stream is ready for framing extraction. Any bit stream coding, like
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* NRZI, Manchester, etc should be done prior this block.
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*
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* @param variant the framing variant
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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 sysnchronization 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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* @param frame_size_field_len the length of the field describing the frame
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* length. I most cases should be 1 or 2.
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*
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* @param frame_len if the variant dictates a constant frame length, this
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* parameter provides the length of the frame
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*
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* @param crc the CRC scheme to use
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* @param descrambler the descramble used
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* @param max_frame_len the maximum allowed frame length
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* @return a shared pointer of a frame_acquisition block
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*/
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static sptr
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make(variant_t variant,
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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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size_t frame_size_field_len,
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size_t frame_len,
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checksum_t crc = CRC_NONE,
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whitening::whitening_sptr descrambler = nullptr,
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size_t max_frame_len = 2048);
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};
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} // namespace satnogs
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} // namespace gr
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#endif /* INCLUDED_SATNOGS_FRAME_ACQUISITION_H */
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