mirror of
https://github.com/eried/portapack-mayhem.git
synced 2024-10-01 01:26:06 -04:00
237 lines
6.8 KiB
C++
237 lines
6.8 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 "sine_table.hpp"
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#include <math.h>
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namespace adsb {
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void make_frame_adsb(ADSBFrame& frame, const uint32_t ICAO_address) {
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frame.clear();
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frame.push_byte((DF_ADSB << 3) | 5); // DF and CA
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frame.push_byte(ICAO_address >> 16);
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frame.push_byte(ICAO_address >> 8);
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frame.push_byte(ICAO_address & 0xFF);
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}
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void encode_frame_id(ADSBFrame& frame, const uint32_t ICAO_address, const std::string& 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_adsb(frame, ICAO_address);
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frame.push_byte(TC_IDENT << 3); // No aircraft category
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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 <<= 6;
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callsign_coded |= s;
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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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frame.push_byte((callsign_coded >> ((5 - c) * 8)) & 0xFF);
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frame.make_CRC();
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}
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/*void generate_frame_emergency(ADSBFrame& frame, const uint32_t ICAO_address, const uint8_t code) {
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make_frame_mode_s(frame, ICAO_address);
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frame.push_byte((28 << 3) + 1); // TC = 28 (Emergency), subtype = 1 (Emergency)
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frame.push_byte(code << 5);
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frame.make_CRC();
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}*/
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void encode_frame_squawk(ADSBFrame& frame, const uint32_t squawk) {
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uint32_t squawk_coded;
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frame.clear();
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frame.push_byte(DF_EHS_SQUAWK << 3); // DF
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frame.push_byte(0);
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// 12 11 10 9 8 7 6 5 4 3 2 1 0
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// 31 30 29 28 27 26 25 24 23 22 21 20 19
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// D4 B4 D2 B2 D1 B1 __ A4 C4 A2 C2 A1 C1
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// ABCD = code (octal, 0000~7777)
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// FEDCBA9876543210
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// xAAAxBBBxCCCxDDD
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// x421x421x421x421
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squawk_coded = ((squawk << 10) & 0x1000) | // D4
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((squawk << 1) & 0x0800) | // B4
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((squawk << 9) & 0x0400) | // D2
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((squawk << 0) & 0x0200) | // B2
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((squawk << 8) & 0x0100) | // D1
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((squawk >> 1) & 0x0080) | // B1
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((squawk >> 9) & 0x0020) | // A4
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((squawk >> 2) & 0x0010) | // C4
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((squawk >> 10) & 0x0008) | // A2
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((squawk >> 3) & 0x0004) | // C2
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((squawk >> 11) & 0x0002) | // A1
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((squawk >> 4) & 0x0001); // C1
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frame.push_byte(squawk_coded >> 5);
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frame.push_byte(squawk_coded << 3);
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frame.make_CRC();
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}
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float cpr_mod(float a, float b) {
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return a - (b * floor(a / b));
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}
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int cpr_NL(float lat) {
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if (lat < 0)
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lat = -lat; // Symmetry
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for (size_t c = 0; c < 58; c++) {
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if (lat < adsb_lat_lut[c])
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return 59 - c;
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}
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return 1;
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}
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int cpr_N(float lat, int is_odd) {
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int nl = cpr_NL(lat) - is_odd;
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if (nl < 1)
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nl = 1;
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return nl;
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}
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// Decoding method (from dump1090):
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// index int j = floor(((59 * latcprE - 60 * latcprO) / 131072) + 0.50)
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// latE = DlatE * (cpr_mod(j, 60) + (latcprE / 131072))
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// latO = DlatO * (cpr_mod(j, 59) + (latcprO / 131072))
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// if latE >= 270 -> latE -= 360
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// if latO >= 270 -> latO -= 360
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// if (cpr_NL(latE) != cpr_NL(latO)) return;
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// int ni = cpr_N(latE ,0);
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// int m = floor((((loncprE * (cpr_NL(latE) - 1)) - (loncprO * cpr_NL(latE))) / 131072) + 0.5)
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// lon = cpr_Dlon(latE, 0) * (cpr_mod(m, ni) + loncprE / 131072);
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// lat = latE;
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// ... or ...
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// int ni = cpr_N(latO ,0);
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// int m = floor((((loncprE * (cpr_NL(latO) - 1)) - (loncprO * cpr_NL(latO))) / 131072) + 0.5)
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// lon = cpr_Dlon(latO, 0) * (cpr_mod(m, ni) + loncprO / 131072);
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// lat = latO;
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// ... and ...
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// if (lon > 180) lon -= 360;
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void encode_frame_pos(ADSBFrame& frame, const uint32_t ICAO_address, const uint32_t altitude,
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const float latitude, const float longitude, const uint32_t 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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make_frame_adsb(frame, ICAO_address);
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frame.push_byte(TC_AIRBORNE_POS << 3); // Bits 2~1: Surveillance Status, bit 0: NICsb
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altitude_coded = (altitude + 1000) / 25; // 25ft precision, insert Q-bit (1)
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altitude_coded = ((altitude_coded & 0x7F0) << 1) | 0x10 | (altitude_coded & 0x0F);
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frame.push_byte(altitude_coded >> 4); // Top-most altitude bits
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// CPR encoding
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// Info from: http://antena.fe.uni-lj.si/literatura/Razno/Avionika/modes/CPRencoding.pdf
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delta_lat = 360.0 / ((4.0 * 15.0) - time_parity); // NZ = 15
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yz = floor(131072.0 * (cpr_mod(latitude, delta_lat) / delta_lat) + 0.5);
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rlat = delta_lat * ((yz / 131072.0) + floor(latitude / delta_lat));
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if ((cpr_NL(rlat) - time_parity) > 0)
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delta_lon = 360.0 / cpr_N(rlat, time_parity);
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else
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delta_lon = 360.0;
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xz = floor(131072.0 * (cpr_mod(longitude, delta_lon) / delta_lon) + 0.5);
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lat = cpr_mod(yz, 131072.0);
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lon = cpr_mod(xz, 131072.0);
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frame.push_byte((altitude_coded << 4) | ((uint32_t)time_parity << 2) | (lat >> 15)); // T = 0
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frame.push_byte(lat >> 7);
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frame.push_byte((lat << 1) | (lon >> 16));
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frame.push_byte(lon >> 8);
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frame.push_byte(lon);
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frame.make_CRC();
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}
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// speed is in knots
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// vertical rate is in ft/min
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void encode_frame_velo(ADSBFrame& frame, const uint32_t ICAO_address, const uint32_t speed,
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const float angle, const int32_t v_rate) {
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int32_t velo_ew, velo_ns, v_rate_coded;
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uint32_t velo_ew_abs, velo_ns_abs, v_rate_coded_abs;
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// To get NS and EW speeds from speed and bearing, a polar to cartesian conversion is enough
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velo_ew = static_cast<int32_t>(sin_f32(DEG_TO_RAD(angle) + (pi / 2)) * speed);
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velo_ns = static_cast<int32_t>(sin_f32(DEG_TO_RAD(angle)) * speed);
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v_rate_coded = (v_rate / 64) + 1;
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velo_ew_abs = abs(velo_ew);
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velo_ns_abs = abs(velo_ns);
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v_rate_coded_abs = abs(v_rate_coded);
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make_frame_adsb(frame, ICAO_address);
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frame.push_byte((TC_AIRBORNE_VELO << 3) | 1); // Subtype: 1 (subsonic)
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frame.push_byte(((velo_ew < 0 ? 1 : 0) << 2) | (velo_ew_abs >> 8));
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frame.push_byte(velo_ew_abs);
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frame.push_byte(((velo_ns < 0 ? 1 : 0) << 7) | (velo_ns_abs >> 3));
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frame.push_byte((velo_ns_abs << 5) | ((v_rate_coded < 0 ? 1 : 0) << 3) | (v_rate_coded_abs >> 6)); // VrSrc = 0
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frame.push_byte(v_rate_coded_abs << 2);
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frame.push_byte(0);
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frame.make_CRC();
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}
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} /* namespace adsb */
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