mirror of
https://github.com/eried/portapack-mayhem.git
synced 2024-10-01 01:26:06 -04:00
147 lines
4.1 KiB
C++
147 lines
4.1 KiB
C++
/*
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* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
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* Copyright (C) 2016 Furrtek
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*
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* This file is part of PortaPack.
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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 2, or (at your option)
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* 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; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#include "adsb.hpp"
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#include "portapack_persistent_memory.hpp"
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namespace adsb {
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void make_frame_mode_s(uint8_t * const adsb_frame, const uint32_t ICAO_address) {
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adsb_frame[0] = (17 << 3) | 5; // DF and CA
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adsb_frame[1] = ICAO_address >> 16;
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adsb_frame[2] = (ICAO_address >> 8) & 0xFF;
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adsb_frame[3] = ICAO_address & 0xFF;
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memset(&adsb_frame[4], 0, 10);
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}
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void generate_frame_id(uint8_t * const adsb_frame, const uint32_t ICAO_address, char * const callsign) {
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std::string callsign_formatted(8, '_');
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uint64_t callsign_coded = 0;
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uint32_t c, s;
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char ch;
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make_frame_mode_s(adsb_frame, ICAO_address);
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adsb_frame[4] = 4 << 3; // TC = 4: Aircraft ID
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// Translate and encode callsign
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for (c = 0; c < 8; c++) {
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ch = callsign[c];
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for (s = 0; s < 64; s++)
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if (ch == icao_id_lut[s]) break;
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if (s >= 64) {
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ch = ' '; // Invalid character
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s = 32;
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}
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callsign_coded |= ((uint64_t)s << ((7 - c) * 6));
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callsign[c] = ch;
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}
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// Insert callsign in frame
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for (c = 0; c < 6; c++)
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adsb_frame[c + 5] = (callsign_coded >> ((5 - c) * 8)) & 0xFF;
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ADSB_generate_CRC(adsb_frame);
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}
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void generate_frame_emergency(uint8_t * const adsb_frame, const uint32_t ICAO_address, const uint8_t code) {
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make_frame_mode_s(adsb_frame, ICAO_address);
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adsb_frame[4] = (28 << 3) + 1; // TC = 28 (Emergency), subtype = 1 (Emergency)
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adsb_frame[5] = code << 5;
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ADSB_generate_CRC(adsb_frame);
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}
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void generate_frame_pos(uint8_t * const adsb_frame, const uint32_t ICAO_address, const uint32_t altitude,
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const float latitude, const float longitude) {
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uint8_t c, time_parity;
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uint32_t altitude_coded;
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uint32_t LAT, LON;
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float delta_lat, yz, rlat, delta_lon, xz;
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LAT = 0;
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make_frame_mode_s(adsb_frame, ICAO_address);
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adsb_frame[4] = 11 << 3; // TC = 11: Airborne position
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altitude_coded = (altitude + 1000) / 25; // Can be coded in 100ft steps also
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// LAT:
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// index j = floor(59*latcprE-60*latcprO+0.50)
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// latE = DlatE*(mod(j,60)+latcprE)
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// latO = DlatO*(mod(j,59)+latcprO)
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// if latE >= 270 -> latE -= 360
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// if latO >= 270 -> latO -= 360
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//time_parity = 0; // 0~1
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//delta_lat = 90.0 / (60.0 - (time_parity / 4.0));
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//yz = 524288.0 * (mod(lat, delta_lat) / delta_lat); // Round to int !
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//rlat = delta_lat * ((yz / 524288.0) + int(lat / delta_lat));
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//delta_lon = 360.0 / (NL(rlat) - time_parity);
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//xz = 524288.0 * (mod(lon, delta_lon) / delta_lon); // Round to int !
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/*if (time_parity) {
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A = sign(rlat0)[NL(rlat0) - NL(rlat1)];
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}*/
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// int xz and yz, then:
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// xz >>= 2;
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// yz >>= 2;
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// To get 17 bits
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// aaaaaaa Q bbbb
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adsb_frame[5] = ((altitude_coded & 0x7F0) >> 3) | 1;
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adsb_frame[6] = ((altitude_coded & 0x00F) << 4) | (LAT >> 15); // Then 0, even/odd, and the 2 LAT-CPR MSBs
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}
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void ADSB_generate_CRC(uint8_t * const in_frame) {
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uint8_t adsb_crc[14]; // Temp buffer
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uint8_t b, c, s, bitn;
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const uint32_t crc_poly = 0x1205FFF;
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in_frame[11] = 0x00; // Clear CRC
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in_frame[12] = 0x00;
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in_frame[13] = 0x00;
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// Compute CRC
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memcpy(adsb_crc, in_frame, 14);
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for (c = 0; c < 11; c++) {
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for (b = 0; b < 8; b++) {
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if ((adsb_crc[c] << b) & 0x80) {
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for (s = 0; s < 25; s++) {
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bitn = (c * 8) + b + s;
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if ((crc_poly >> s) & 1) adsb_crc[bitn >> 3] ^= (0x80 >> (bitn & 7));
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}
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}
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}
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}
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// Insert CRC in frame
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memcpy(&in_frame[11], &adsb_crc[11], 3);
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}
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} /* namespace adsb */
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