mirror of
https://github.com/f4exb/sdrangel.git
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98 lines
3.9 KiB
C++
98 lines
3.9 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2021 Edouard Griffiths, F4EXB //
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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 as 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 V3 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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// Source: https://mmi-comm.tripod.com/dcs.html //
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///////////////////////////////////////////////////////////////////////////////////
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#include <bitset>
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#include "nfmmoddcs.h"
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const float NFMModDCS::m_codeRate = 134.3; //!< bits per second
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NFMModDCS::NFMModDCS()
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{
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reset();
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}
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NFMModDCS::~NFMModDCS()
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{
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}
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void NFMModDCS::reset()
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{
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m_step = 0;
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}
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void NFMModDCS::setDCS(int code)
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{
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unsigned int dcsCode = code < 0 ? 0 : code > 511 ? 511 : code; // trim invalid values
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// Parity bits calculation:
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unsigned int p[11];
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p[0] = std::bitset<32>(dcsCode & 0b10011111).count() % 2; // P0 = C0 + C1 + C2 + C3 + C4 + C7 (modulo two addition)
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p[1] = (std::bitset<32>(dcsCode & 0b100111110).count()+1) % 2; // P1 = NOT ( C1 + C2 + C3 + C4 + C5 + C8 )
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p[2] = std::bitset<32>(dcsCode & 0b11100011).count() % 2; // P2 = C0 + C1 + C5 + C6 + C7
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p[3] = (std::bitset<32>(dcsCode & 0b111000110).count()+1) % 2; // P3 = NOT ( C1 + C2 + C6 + C7 + C8 )
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p[4] = (std::bitset<32>(dcsCode & 0b100010011).count()+1) % 2; // P4 = NOT ( C0 + C1 + C4 + C8 )
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p[5] = (std::bitset<32>(dcsCode & 0b10111001).count()+1) % 2; // P5 = NOT ( C0 + C3 + C4 + C5 + C7 )
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p[6] = std::bitset<32>(dcsCode & 0b111101101).count() % 2; // P6 = C0 + C2 + C3 + C5 + C6 + C7 + C8
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p[7] = std::bitset<32>(dcsCode & 0b111011010).count() % 2; // P7 = C1 + C3 + C4 + C6 + C7 + C8
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p[8] = std::bitset<32>(dcsCode & 0b110110100).count() % 2; // P8 = C2 + C4 + C5 + C7 + C8
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p[9] = (std::bitset<32>(dcsCode & 0b101101000).count()+1) % 2; // P9 = NOT ( C3 + C5 + C6 + C8 )
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p[10] = (std::bitset<32>(dcsCode & 0b1001111).count()+1) % 2; // P10 = NOT ( C0 + C1 + C2 + C3 + C6 )
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int dcsIndex = 0;
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// code:
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for (int i = 0; i < 9; i++, dcsIndex++) {
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m_dcsWord[dcsIndex] = (dcsCode >> i) & 1;
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}
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// filler (0x04)
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m_dcsWord[dcsIndex++] = 0;
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m_dcsWord[dcsIndex++] = 0;
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m_dcsWord[dcsIndex++] = 1;
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// parity
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for (int i = 0; i < 11; i++, dcsIndex++) {
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m_dcsWord[dcsIndex] = p[i];
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}
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m_step = 0;
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}
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void NFMModDCS::setPositive(bool positive)
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{
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m_positive = positive;
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m_step = 0;
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}
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void NFMModDCS::setSampleRate(int sampleRate)
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{
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m_bitPerStep = m_codeRate / sampleRate;
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m_step = 0;
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}
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int NFMModDCS::next()
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{
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int dcsIndex = (int) m_step;
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int carrier = (m_dcsWord[dcsIndex] == 1) ? (m_positive ? 1 : -1) : (m_positive ? -1 : 1);
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if (m_step + m_bitPerStep < 23) {
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m_step += m_bitPerStep;
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} else {
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m_step = m_step + m_bitPerStep - 23;
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}
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return carrier;
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}
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