M17 transmitter class
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Silvano Seva
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39e41ee470
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/***************************************************************************
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* Copyright (C) 2021 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 M17TRANSMITTER_H
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#define M17TRANSMITTER_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 <string>
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#include <array>
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#include "M17ConvolutionalEncoder.h"
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#include "M17LinkSetupFrame.h"
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#include "M17Frame.h"
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#include "M17Modulator.h"
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/**
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* M17 transmitter.
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*/
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class M17Transmitter
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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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* @param modulator: reference to M17 4FSK modulator driver.
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*/
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M17Transmitter(M17Modulator& modulator);
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/**
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* Destructor.
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*/
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~M17Transmitter();
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/**
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* Start a new data stream with broadcast destination callsign.
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*
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* @param src: source callsign.
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*/
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void start(const std::string& src);
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/**
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* Start a new data stream with given destination callsign. If destination
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* callsing is empty, the stream falls back to broadcast transmission.
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*
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* @param src: source callsign.
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* @param dst: destination callsign.
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*/
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void start(const std::string& src, const std::string& dst);
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/**
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* Send a block of data.
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*
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* @param payload: payload data.
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* @param isLast: if true, current frame is marked as the last one to be
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* transmitted.
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*/
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void send(const payload_t& payload, const bool isLast = false);
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private:
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M17ConvolutionalEncoder encoder; ///< Convolutional encoder.
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M17LinkSetupFrame lsf; ///< Link Setup Frame handler.
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M17Frame dataFrame; ///< Data frame Handler.
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M17Modulator& modulator; ///< 4FSK modulator.
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std::array< lich_t, 6 > lichSegments; ///< Encoded LSF chunks for LICH generation.
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uint8_t currentLich; ///< Index of current LSF chunk.
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uint16_t frameNumber; ///< Current frame number.
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};
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#endif /* M17TRANSMITTER_H */
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/***************************************************************************
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* Copyright (C) 2021 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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#include <M17/M17CodePuncturing.h>
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#include <M17/M17Decorrelator.h>
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#include <M17/M17Interleaver.h>
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#include <M17/M17Transmitter.h>
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static constexpr std::array<uint8_t, 2> LSF_SYNC_WORD = {0x55, 0xF7};
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static constexpr std::array<uint8_t, 2> DATA_SYNC_WORD = {0xFF, 0x5D};
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M17Transmitter::M17Transmitter(M17Modulator& modulator) : modulator(modulator),
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currentLich(0), frameNumber(0)
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{
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}
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M17Transmitter::~M17Transmitter()
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{
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}
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void M17Transmitter::start(const std::string& src)
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{
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// Just call start() with an empty string for destination callsign.
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std::string empty;
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start(src, empty);
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}
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void M17Transmitter::start(const std::string& src, const std::string& dst)
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{
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// Reset LICH and frame counters
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currentLich = 0;
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frameNumber = 0;
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// Fill the Link Setup Frame
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lsf.clear();
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lsf.setSource(src);
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if(!dst.empty()) lsf.setDestination(dst);
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streamType_t type;
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type.stream = 1; // Stream
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type.dataType = 2; // Voice data
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type.CAN = 0xA; // Channel access number
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lsf.setType(type);
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lsf.updateCrc();
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// Generate the Golay(24,12) LICH segments
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for(size_t i = 0; i < lichSegments.size(); i++)
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{
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lichSegments[i] = lsf.generateLichSegment(i);
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}
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// Encode the LSF, then puncture and decorrelate its data
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std::array<uint8_t, 61> encoded;
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encoder.reset();
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encoder.encode(&lsf.getData(), encoded.data(), sizeof(lsf_t));
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encoded[60] = encoder.flush();
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std::array<uint8_t, 46> punctured;
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puncture(encoded, punctured, LSF_puncture);
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interleave(punctured);
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decorrelate(punctured);
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// Send preamble
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std::array<uint8_t, 2> preamble_sync;
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std::array<uint8_t, 46> preamble_bytes;
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preamble_sync.fill(0x77);
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preamble_bytes.fill(0x77);
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modulator.send(preamble_sync, preamble_bytes);
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// Send LSF
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modulator.send(LSF_SYNC_WORD, punctured);
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}
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void M17Transmitter::send(const payload_t& payload, const bool isLast)
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{
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dataFrame.clear();
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dataFrame.setFrameNumber(frameNumber);
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frameNumber = (frameNumber + 1) & 0x07FF;
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if(isLast) dataFrame.lastFrame();
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std::copy(payload.begin(), payload.end(), dataFrame.payload().begin());
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// Encode frame
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std::array<uint8_t, 37> encoded;
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encoder.reset();
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encoder.encode(&dataFrame.getData(), encoded.data(), sizeof(dataFrame_t));
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encoded[36] = encoder.flush();
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std::array<uint8_t, 34> punctured;
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puncture(encoded, punctured, Audio_puncture);
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// Add LICH segment to coded data and send
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std::array<uint8_t, 46> frame;
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auto it = std::copy(lichSegments[currentLich].begin(),
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lichSegments[currentLich].end(),
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frame.begin());
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std::copy(punctured.begin(), punctured.end(), it);
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// Increment LICH counter after copy
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currentLich = (currentLich + 1) % lichSegments.size();
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interleave(frame);
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decorrelate(frame);
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modulator.send(DATA_SYNC_WORD, frame);
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}
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