mayhem-firmware/firmware/application/protocols/adsb.cpp
furrtek bebec9ccf7 More ADS-B TX experimentation
Lots of junk added in Numbers Station regarding voice files
Removed warnings caused by unfinished ADS-B function
2017-05-01 10:42:09 +01:00

149 lines
4.1 KiB
C++

/*
* Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
* Copyright (C) 2016 Furrtek
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include "adsb.hpp"
#include "portapack_persistent_memory.hpp"
namespace adsb {
void make_frame_mode_s(uint8_t * const adsb_frame, const uint32_t ICAO_address) {
adsb_frame[0] = (17 << 3) | 5; // DF and CA
adsb_frame[1] = ICAO_address >> 16;
adsb_frame[2] = (ICAO_address >> 8) & 0xFF;
adsb_frame[3] = ICAO_address & 0xFF;
memset(&adsb_frame[4], 0, 10);
}
void generate_frame_id(uint8_t * const adsb_frame, const uint32_t ICAO_address, std::string & callsign) {
std::string callsign_formatted(8, '_');
uint64_t callsign_coded = 0;
uint32_t c, s;
char ch;
make_frame_mode_s(adsb_frame, ICAO_address);
adsb_frame[4] = 4 << 3; // TC = 4: Aircraft ID
// Translate and encode callsign
for (c = 0; c < 8; c++) {
ch = callsign[c];
for (s = 0; s < 64; s++)
if (ch == icao_id_lut[s]) break;
if (s >= 64) {
ch = ' '; // Invalid character
s = 32;
}
callsign_coded |= ((uint64_t)s << ((7 - c) * 6));
callsign[c] = ch;
}
// Insert callsign in frame
for (c = 0; c < 6; c++)
adsb_frame[c + 5] = (callsign_coded >> ((5 - c) * 8)) & 0xFF;
ADSB_generate_CRC(adsb_frame);
}
void generate_frame_emergency(uint8_t * const adsb_frame, const uint32_t ICAO_address, const uint8_t code) {
make_frame_mode_s(adsb_frame, ICAO_address);
adsb_frame[4] = (28 << 3) + 1; // TC = 28 (Emergency), subtype = 1 (Emergency)
adsb_frame[5] = code << 5;
ADSB_generate_CRC(adsb_frame);
}
/*
void generate_frame_pos(uint8_t * const adsb_frame, const uint32_t ICAO_address, const uint32_t altitude,
const float latitude, const float longitude) {
uint8_t c, time_parity;
uint32_t altitude_coded;
uint32_t LAT, LON;
float delta_lat, yz, rlat, delta_lon, xz;
LAT = 0;
make_frame_mode_s(adsb_frame, ICAO_address);
adsb_frame[4] = 11 << 3; // TC = 11: Airborne position
altitude_coded = (altitude + 1000) / 25; // Can be coded in 100ft steps also
// LAT:
// index j = floor(59*latcprE-60*latcprO+0.50)
// latE = DlatE*(mod(j,60)+latcprE)
// latO = DlatO*(mod(j,59)+latcprO)
// if latE >= 270 -> latE -= 360
// if latO >= 270 -> latO -= 360
//time_parity = 0; // 0~1
//delta_lat = 90.0 / (60.0 - (time_parity / 4.0));
//yz = 524288.0 * (mod(lat, delta_lat) / delta_lat); // Round to int !
//rlat = delta_lat * ((yz / 524288.0) + int(lat / delta_lat));
//delta_lon = 360.0 / (NL(rlat) - time_parity);
//xz = 524288.0 * (mod(lon, delta_lon) / delta_lon); // Round to int !
if (time_parity) {
A = sign(rlat0)[NL(rlat0) - NL(rlat1)];
}
// int xz and yz, then:
// xz >>= 2;
// yz >>= 2;
// To get 17 bits
// aaaaaaa Q bbbb
adsb_frame[5] = ((altitude_coded & 0x7F0) >> 3) | 1;
adsb_frame[6] = ((altitude_coded & 0x00F) << 4) | (LAT >> 15); // Then 0, even/odd, and the 2 LAT-CPR MSBs
}
*/
void ADSB_generate_CRC(uint8_t * const in_frame) {
uint8_t adsb_crc[14]; // Temp buffer
uint8_t b, c, s, bitn;
const uint32_t crc_poly = 0x1205FFF;
// Clear CRC
in_frame[11] = 0x00;
in_frame[12] = 0x00;
in_frame[13] = 0x00;
// Compute CRC
memcpy(adsb_crc, in_frame, 14);
for (c = 0; c < 11; c++) {
for (b = 0; b < 8; b++) {
if ((adsb_crc[c] << b) & 0x80) {
for (s = 0; s < 25; s++) {
bitn = (c * 8) + b + s;
if ((crc_poly >> s) & 1) adsb_crc[bitn >> 3] ^= (0x80 >> (bitn & 7));
}
}
}
}
// Insert CRC in frame
memcpy(&in_frame[11], &adsb_crc[11], 3);
}
} /* namespace adsb */