kopia lustrzana https://github.com/OpenRTX/OpenRTX
133 wiersze
4.4 KiB
C++
133 wiersze
4.4 KiB
C++
/***************************************************************************
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* Copyright (C) 2021 - 2022 by Federico Amedeo Izzo IU2NUO, *
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* Niccolò Izzo IU2KIN *
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* Frederik Saraci IU2NRO *
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* Silvano Seva IU2KWO *
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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 M17_MODULATOR_H
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#define M17_MODULATOR_H
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#ifndef __cplusplus
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#error This header is C++ only!
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#endif
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#include <interfaces/audio_stream.h>
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#include <cstdint>
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#include <array>
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namespace M17
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{
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/**
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* Modulator device for M17 protocol.
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*/
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class M17Modulator
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{
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public:
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/**
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* Constructor.
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*/
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M17Modulator();
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/**
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* Destructor.
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*/
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~M17Modulator();
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/**
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* Allocate buffers for baseband audio generation and initialise modulator.
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*/
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void init();
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/**
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* Shutdown modulator and deallocate data buffers.
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*/
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void terminate();
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/**
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* Generate and transmit the baseband signal obtained by 4FSK modulation of
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* a given block of data. When called for the first time, this function
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* starts baseband transmission.
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*
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* @param sync: synchronisation word to be prepended to data block.
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* @param data: data block to be transmitted.
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* @param isLast: flag signalling that current block is the last one being
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* transmitted.
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*/
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void send(const std::array< uint8_t, 2 >& sync,
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const std::array< uint8_t, 46 >& data,
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const bool isLast = false);
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private:
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/**
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* Generate baseband stream from symbol stream.
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*/
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void generateBaseband();
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/**
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* Emit the baseband stream towards the output stage, platform dependent.
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*/
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void emitBaseband();
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/**
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* Utility function to encode a given byte of data into 4FSK symbols. Each
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* byte is encoded in four symbols.
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*
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* @param value: value to be encoded in 4FSK symbols.
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* @return std::array containing the four symbols obtained by 4FSK encoding.
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*/
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inline std::array< int8_t, 4 > byteToSymbols(uint8_t value)
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{
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static constexpr int8_t LUT[] = { +1, +3, -1, -3};
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std::array< int8_t, 4 > symbols;
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symbols[3] = LUT[value & 0x03];
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value >>= 2;
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symbols[2] = LUT[value & 0x03];
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value >>= 2;
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symbols[1] = LUT[value & 0x03];
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value >>= 2;
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symbols[0] = LUT[value & 0x03];
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return symbols;
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}
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static constexpr size_t M17_TX_SAMPLE_RATE = 48000;
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static constexpr size_t M17_FRAME_SAMPLES_48K = 1920;
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static constexpr size_t M17_FRAME_SYMBOLS = 192;
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#ifdef PLATFORM_MOD17
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static constexpr float M17_RRC_GAIN = 15000.0f;
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static constexpr float M17_RRC_OFFSET = 11500.0f;
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#else
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static constexpr float M17_RRC_GAIN = 7168.0f;
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static constexpr float M17_RRC_OFFSET = 0.0f;
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#endif
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std::array< int16_t, M17_FRAME_SYMBOLS > symbols;
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stream_sample_t *baseband_buffer; ///< Buffer for baseband audio handling.
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stream_sample_t *idleBuffer; ///< Half baseband buffer, free for processing.
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streamId outStream; ///< Baseband output stream ID.
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bool txRunning; ///< Transmission running.
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bool stopTx; ///< Stop transmission request.
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};
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} /* M17 */
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#endif /* M17_MODULATOR_H */
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