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dump1090/dump1090.c

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/* dump1090, a Mode S messages decoder for RTLSDR devices.
*
* Copyright (C) 2012 by Salvatore Sanfilippo <antirez@gmail.com>
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _WIN32
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <pthread.h>
#include <stdint.h>
#include <errno.h>
#include <unistd.h>
#include <math.h>
#include <sys/time.h>
#include <sys/timeb.h>
#include <signal.h>
#include <fcntl.h>
#include <ctype.h>
#include <sys/stat.h>
#include "rtl-sdr.h"
#include "anet.h"
#else
#include "dump1090.h" //Put everything Windows specific in here
#include "rtl-sdr.h"
#endif
// File Version number
// ====================
// Format is : MajorVer.MinorVer.DayMonth.Year"
// MajorVer changes only with significant changes
// MinorVer changes when additional features are added, but not for bug fixes (range 00-99)
// DayDate & Year changes for all changes, including for bug fixes. It represent the release date of the update
//
#define MODES_DUMP1090_VERSION "1.05.1305.13"
#define MODES_USER_LATITUDE_DFLT (0.0)
#define MODES_USER_LONGITUDE_DFLT (0.0)
#define MODES_DEFAULT_RATE 2000000
#define MODES_DEFAULT_FREQ 1090000000
#define MODES_DEFAULT_WIDTH 1000
#define MODES_DEFAULT_HEIGHT 700
#define MODES_ASYNC_BUF_NUMBER 12
#define MODES_ASYNC_BUF_SIZE (16*16384) /* 256k */
#define MODES_ASYNC_BUF_SAMPLES (MODES_ASYNC_BUF_SIZE / 2) /* Each sample is 2 bytes */
#define MODES_AUTO_GAIN -100 /* Use automatic gain. */
#define MODES_MAX_GAIN 999999 /* Use max available gain. */
#define MODES_MSG_SQUELCH_LEVEL 0x02FF /* Average signal strength limit */
#define MODES_MSG_ENCODER_ERRS 3 /* Maximum number of encoding errors */
#define MODEAC_MSG_SAMPLES (25 * 2) /* include up to the SPI bit */
#define MODEAC_MSG_BYTES 2
#define MODEAC_MSG_SQUELCH_LEVEL 0x07FF /* Average signal strength limit */
#define MODEAC_MSG_FLAG (1<<0)
#define MODEAC_MSG_MODES_HIT (1<<1)
#define MODEAC_MSG_MODEA_HIT (1<<2)
#define MODEAC_MSG_MODEC_HIT (1<<3)
#define MODEAC_MSG_MODEA_ONLY (1<<4)
#define MODEAC_MSG_MODEC_OLD (1<<5)
#define MODES_PREAMBLE_US 8 /* microseconds = bits */
#define MODES_PREAMBLE_SAMPLES (MODES_PREAMBLE_US * 2)
#define MODES_PREAMBLE_SIZE (MODES_PREAMBLE_SAMPLES * sizeof(uint16_t))
#define MODES_LONG_MSG_BYTES 14
#define MODES_SHORT_MSG_BYTES 7
#define MODES_LONG_MSG_BITS (MODES_LONG_MSG_BYTES * 8)
#define MODES_SHORT_MSG_BITS (MODES_SHORT_MSG_BYTES * 8)
#define MODES_LONG_MSG_SAMPLES (MODES_LONG_MSG_BITS * 2)
#define MODES_SHORT_MSG_SAMPLES (MODES_SHORT_MSG_BITS * 2)
#define MODES_LONG_MSG_SIZE (MODES_LONG_MSG_SAMPLES * sizeof(uint16_t))
#define MODES_SHORT_MSG_SIZE (MODES_SHORT_MSG_SAMPLES * sizeof(uint16_t))
#define MODES_RAWOUT_BUF_SIZE (1500)
#define MODES_RAWOUT_BUF_FLUSH (MODES_RAWOUT_BUF_SIZE - 200)
#define MODES_RAWOUT_BUF_RATE (1000) // 1000 * 64mS = 1 Min approx
#define MODES_ICAO_CACHE_LEN 1024 /* Power of two required. */
#define MODES_ICAO_CACHE_TTL 60 /* Time to live of cached addresses. */
#define MODES_UNIT_FEET 0
#define MODES_UNIT_METERS 1
#define MODES_USER_LATLON_VALID (1<<0)
#define MODES_ACFLAGS_LATLON_VALID (1<<0) // Aircraft Lat/Lon is decoded
#define MODES_ACFLAGS_ALTITUDE_VALID (1<<1) // Aircraft altitude is known
#define MODES_ACFLAGS_HEADING_VALID (1<<2) // Aircraft heading is known
#define MODES_ACFLAGS_SPEED_VALID (1<<3) // Aircraft speed is known
#define MODES_ACFLAGS_VERTRATE_VALID (1<<4) // Aircraft vertical rate is known
#define MODES_ACFLAGS_SQUAWK_VALID (1<<5) // Aircraft Mode A Squawk is known
#define MODES_ACFLAGS_CALLSIGN_VALID (1<<6) // Aircraft Callsign Identity
#define MODES_ACFLAGS_EWSPEED_VALID (1<<7) // Aircraft East West Speed is known
#define MODES_ACFLAGS_NSSPEED_VALID (1<<8) // Aircraft North South Speed is known
#define MODES_ACFLAGS_AOG (1<<9) // Aircraft is On the Ground
#define MODES_ACFLAGS_LLEVEN_VALID (1<<10) // Aircraft Even Lot/Lon is known
#define MODES_ACFLAGS_LLODD_VALID (1<<11) // Aircraft Odd Lot/Lon is known
#define MODES_ACFLAGS_AOG_VALID (1<<12) // MODES_ACFLAGS_AOG is valid
#define MODES_ACFLAGS_FS_VALID (1<<13) // Aircraft Flight Status is known
#define MODES_ACFLAGS_NSEWSPD_VALID (1<<14) // Aircraft EW and NS Speed is known
#define MODES_ACFLAGS_LATLON_REL_OK (1<<15) // Indicates it's OK to do a relative CPR
#define MODES_ACFLAGS_LLEITHER_VALID (MODES_ACFLAGS_LLEVEN_VALID | MODES_ACFLAGS_LLODD_VALID)
#define MODES_ACFLAGS_LLBOTH_VALID (MODES_ACFLAGS_LLEVEN_VALID | MODES_ACFLAGS_LLODD_VALID)
#define MODES_ACFLAGS_AOG_GROUND (MODES_ACFLAGS_AOG_VALID | MODES_ACFLAGS_AOG)
#define MODES_DEBUG_DEMOD (1<<0)
#define MODES_DEBUG_DEMODERR (1<<1)
#define MODES_DEBUG_BADCRC (1<<2)
#define MODES_DEBUG_GOODCRC (1<<3)
#define MODES_DEBUG_NOPREAMBLE (1<<4)
#define MODES_DEBUG_NET (1<<5)
#define MODES_DEBUG_JS (1<<6)
/* When debug is set to MODES_DEBUG_NOPREAMBLE, the first sample must be
* at least greater than a given level for us to dump the signal. */
#define MODES_DEBUG_NOPREAMBLE_LEVEL 25
#define MODES_INTERACTIVE_REFRESH_TIME 250 /* Milliseconds */
#define MODES_INTERACTIVE_ROWS 15 /* Rows on screen */
#define MODES_INTERACTIVE_TTL 60 /* TTL before being removed */
#define MODES_NET_MAX_FD 1024
#define MODES_NET_OUTPUT_SBS_PORT 30003
#define MODES_NET_OUTPUT_RAW_PORT 30002
#define MODES_NET_INPUT_RAW_PORT 30001
#define MODES_NET_HTTP_PORT 8080
#define MODES_CLIENT_BUF_SIZE 1024
#define MODES_NET_SNDBUF_SIZE (1024*64)
#define MODES_NOTUSED(V) ((void) V)
/* Structure used to describe a networking client. */
struct client {
int fd; /* File descriptor. */
int service; /* TCP port the client is connected to. */
char buf[MODES_CLIENT_BUF_SIZE+1]; /* Read buffer. */
int buflen; /* Amount of data on buffer. */
};
// Structure used to describe an aircraft in iteractive mode
struct aircraft {
uint32_t addr; // ICAO address
char flight[16]; // Flight number
unsigned char signalLevel[8]; // Last 8 Signal Amplitudes
int altitude; // Altitude
int speed; // Velocity
int track; // Angle of flight
time_t seen; // Time at which the last packet was received
time_t seenLatLon; // Time at which the last lat long was calculated
uint64_t timestamp; // Timestamp at which the last packet was received
uint64_t timestampLatLon; // Timestamp at which the last lat long was calculated
long messages; // Number of Mode S messages received
int modeA; // Squawk
int modeC; // Altitude
long modeAcount; // Mode A Squawk hit Count
long modeCcount; // Mode C Altitude hit Count
int modeACflags; // Flags for mode A/C recognition
// Encoded latitude and longitude as extracted by odd and even CPR encoded messages
int odd_cprlat;
int odd_cprlon;
int even_cprlat;
int even_cprlon;
double lat, lon; // Coordinated obtained from CPR encoded data
int bFlags; // Flags related to valid fields in this structure
uint64_t odd_cprtime, even_cprtime;
struct aircraft *next; // Next aircraft in our linked list
};
/* Program global state. */
struct {
/* Internal state */
pthread_t reader_thread;
pthread_mutex_t data_mutex; /* Mutex to synchronize buffer access. */
pthread_cond_t data_cond; /* Conditional variable associated. */
uint16_t *data; /* Raw IQ samples buffer */
uint16_t *magnitude; /* Magnitude vector */
struct timeb stSystemTimeRTL; /* System time when RTL passed us the Latest block */
uint64_t timestampBlk; /* Timestamp of the start of the current block */
struct timeb stSystemTimeBlk; /* System time when RTL passed us currently processing this block */
int fd; /* --ifile option file descriptor. */
int data_ready; /* Data ready to be processed. */
uint32_t *icao_cache; /* Recently seen ICAO addresses cache. */
uint16_t *maglut; /* I/Q -> Magnitude lookup table. */
int exit; /* Exit from the main loop when true. */
/* RTLSDR */
int dev_index;
int gain;
int enable_agc;
rtlsdr_dev_t *dev;
int freq;
int ppm_error;
/* Networking */
char aneterr[ANET_ERR_LEN];
struct client *clients[MODES_NET_MAX_FD]; /* Our clients. */
int maxfd; /* Greatest fd currently active. */
int sbsos; /* SBS output listening socket. */
int ros; /* Raw output listening socket. */
int ris; /* Raw input listening socket. */
int https; /* HTTP listening socket. */
char * rawOut; /* Buffer for building raw output data */
int rawOutUsed; /* How much if the buffer is currently used */
/* Configuration */
char *filename; /* Input form file, --ifile option. */
int fix_errors; /* Single bit error correction if true. */
int check_crc; /* Only display messages with good CRC. */
int raw; /* Raw output format. */
int beast; /* Beast binary format output. */
int mode_ac; /* Enable decoding of SSR Modes A & C. */
int debug; /* Debugging mode. */
int net; /* Enable networking. */
int net_only; /* Enable just networking. */
int net_output_sbs_port; /* SBS output TCP port. */
int net_output_raw_size; /* Minimum Size of the output raw data */
int net_output_raw_rate; /* Rate (in 64mS increments) of output raw data */
int net_output_raw_rate_count; /* Rate (in 64mS increments) of output raw data */
int net_output_raw_port; /* Raw output TCP port. */
int net_input_raw_port; /* Raw input TCP port. */
int net_http_port; /* HTTP port. */
int quiet; /* Suppress stdout */
int interactive; /* Interactive mode */
int interactive_rows; /* Interactive mode: max number of rows. */
int interactive_ttl; /* Interactive mode: TTL before deletion. */
int stats; /* Print stats at exit in --ifile mode. */
int onlyaddr; /* Print only ICAO addresses. */
int metric; /* Use metric units. */
int aggressive; /* Aggressive detection algorithm. */
int mlat; /* Use Beast ascii format for raw data output, i.e. @...; iso *...; */
int interactive_rtl1090; /* flight table in interactive mode is formatted like RTL1090 */
// User details
double fUserLat; // Users receiver/antenna lat/lon needed for initial surface location
double fUserLon; // Users receiver/antenna lat/lon needed for initial surface location
int bUserFlags; // Flags relating to the user details
/* Interactive mode */
struct aircraft *aircrafts;
uint64_t interactive_last_update; /* Last screen update in milliseconds */
/* Statistics */
unsigned int stat_valid_preamble;
unsigned int stat_demodulated;
unsigned int stat_goodcrc;
unsigned int stat_badcrc;
unsigned int stat_fixed;
unsigned int stat_single_bit_fix;
unsigned int stat_two_bits_fix;
unsigned int stat_http_requests;
unsigned int stat_sbs_connections;
unsigned int stat_out_of_phase;
unsigned int stat_DF_Len_Corrected;
unsigned int stat_DF_Type_Corrected;
unsigned int stat_ModeAC;
} Modes;
// The struct we use to store information about a decoded message.
struct modesMessage {
// Generic fields
unsigned char msg[MODES_LONG_MSG_BYTES]; // Binary message.
int msgbits; // Number of bits in message
int msgtype; // Downlink format #
int crcok; // True if CRC was valid
uint32_t crc; // Message CRC
int correctedbits; // No. of bits corrected
uint32_t addr; // ICAO Address from bytes 1 2 and 3
int phase_corrected; // True if phase correction was applied
uint64_t timestampMsg; // Timestamp of the message
unsigned char signalLevel; // Signal Amplitude
// DF 11
int ca; // Responder capabilities
int iid;
// DF 17
int metype; // Extended squitter message type.
int mesub; // Extended squitter message subtype.
int heading; // Reported by aircraft, or computed from from EW and NS velocity
int raw_latitude; // Non decoded latitude.
int raw_longitude; // Non decoded longitude.
double fLat; // Coordinates obtained from CPR encoded data if/when decoded
double fLon; // Coordinates obtained from CPR encoded data if/when decoded
char flight[16]; // 8 chars flight number.
int ew_velocity; // E/W velocity.
int ns_velocity; // N/S velocity.
int vert_rate; // Vertical rate.
int velocity; // Reported by aircraft, or computed from from EW and NS velocity
// DF4, DF5, DF20, DF21
int fs; // Flight status for DF4,5,20,21
int modeA; // 13 bits identity (Squawk).
// Fields used by multiple message types.
int altitude;
int unit;
int bFlags; // Flags related to fields in this structure
};
void interactiveShowData(void);
struct aircraft* interactiveReceiveData(struct modesMessage *mm);
void modesSendAllClients(int service, void *msg, int len);
void modesSendRawOutput(struct modesMessage *mm);
void modesSendBeastOutput(struct modesMessage *mm);
void modesSendSBSOutput(struct modesMessage *mm);
void useModesMessage(struct modesMessage *mm);
int fixBitErrors(unsigned char *msg, int bits);
int fixSingleBitErrors(unsigned char *msg, int bits);
int fixTwoBitsErrors(unsigned char *msg, int bits);
void modesInitErrorInfo();
int modesMessageLenByType(int type);
/* ============================= Utility functions ========================== */
static uint64_t mstime(void) {
struct timeval tv;
uint64_t mst;
gettimeofday(&tv, NULL);
mst = ((uint64_t)tv.tv_sec)*1000;
mst += tv.tv_usec/1000;
return mst;
}
void sigintHandler(int dummy) {
MODES_NOTUSED(dummy);
Modes.exit = 1; // Signal to threads that we are done
}
/* =============================== Initialization =========================== */
void modesInitConfig(void) {
// Default everything to zero/NULL
memset(&Modes, 0, sizeof(Modes));
// Now initialise things that should not be 0/NULL to their defaults
Modes.gain = MODES_MAX_GAIN;
Modes.freq = MODES_DEFAULT_FREQ;
Modes.check_crc = 1;
Modes.net_output_sbs_port = MODES_NET_OUTPUT_SBS_PORT;
Modes.net_output_raw_port = MODES_NET_OUTPUT_RAW_PORT;
Modes.net_input_raw_port = MODES_NET_INPUT_RAW_PORT;
Modes.net_http_port = MODES_NET_HTTP_PORT;
Modes.interactive_rows = MODES_INTERACTIVE_ROWS;
Modes.interactive_ttl = MODES_INTERACTIVE_TTL;
Modes.fUserLat = MODES_USER_LATITUDE_DFLT;
Modes.fUserLon = MODES_USER_LONGITUDE_DFLT;
}
void modesInit(void) {
int i, q;
pthread_mutex_init(&Modes.data_mutex,NULL);
pthread_cond_init(&Modes.data_cond,NULL);
// Allocate the various buffers used by Modes
if ( ((Modes.icao_cache = (uint32_t *) malloc(sizeof(uint32_t) * MODES_ICAO_CACHE_LEN * 2) ) == NULL) ||
((Modes.data = (uint16_t *) malloc(MODES_ASYNC_BUF_SIZE) ) == NULL) ||
((Modes.magnitude = (uint16_t *) malloc(MODES_ASYNC_BUF_SIZE+MODES_PREAMBLE_SIZE+MODES_LONG_MSG_SIZE) ) == NULL) ||
((Modes.maglut = (uint16_t *) malloc(sizeof(uint16_t) * 256 * 256) ) == NULL) ||
((Modes.rawOut = (char *) malloc(MODES_RAWOUT_BUF_SIZE) ) == NULL) )
{
fprintf(stderr, "Out of memory allocating data buffer.\n");
exit(1);
}
// Clear the buffers that have just been allocated, just in-case
memset(Modes.icao_cache, 0, sizeof(uint32_t) * MODES_ICAO_CACHE_LEN * 2);
memset(Modes.data, 127, MODES_ASYNC_BUF_SIZE);
memset(Modes.magnitude, 0, MODES_ASYNC_BUF_SIZE+MODES_PREAMBLE_SIZE+MODES_LONG_MSG_SIZE);
// Validate the users Lat/Lon home location inputs
if ( (Modes.fUserLat > 90.0) // Latitude must be -90 to +90
|| (Modes.fUserLat < -90.0) // and
|| (Modes.fUserLon > 360.0) // Longitude must be -180 to +360
|| (Modes.fUserLon < -180.0) ) {
Modes.fUserLat = Modes.fUserLon = 0.0;
} else if (Modes.fUserLon > 180.0) { // If Longitude is +180 to +360, make it -180 to 0
Modes.fUserLon -= 360.0;
}
// If both Lat and Lon are 0.0 then the users location is either invalid/not-set, or (s)he's in the
// Atlantic ocean off the west coast of Africa. This is unlikely to be correct.
// Set the user LatLon valid flag only if either Lat or Lon are non zero. Note the Greenwich meridian
// is at 0.0 Lon,so we must check for either fLat or fLon being non zero not both.
// Testing the flag at runtime will be much quicker than ((fLon != 0.0) || (fLat != 0.0))
Modes.bUserFlags &= ~MODES_USER_LATLON_VALID;
if ((Modes.fUserLat != 0.0) || (Modes.fUserLon != 0.0)) {
Modes.bUserFlags |= MODES_USER_LATLON_VALID;
}
// Limit the maximum requested raw output size to less than one Ethernet Block
if (Modes.net_output_raw_size > (MODES_RAWOUT_BUF_FLUSH))
{Modes.net_output_raw_size = MODES_RAWOUT_BUF_FLUSH;}
if (Modes.net_output_raw_rate > (MODES_RAWOUT_BUF_RATE))
{Modes.net_output_raw_rate = MODES_RAWOUT_BUF_RATE;}
// Initialise the Block Timers to something half sensible
ftime(&Modes.stSystemTimeRTL);
Modes.stSystemTimeBlk = Modes.stSystemTimeRTL;
// Each I and Q value varies from 0 to 255, which represents a range from -1 to +1. To get from the
// unsigned (0-255) range you therefore subtract 127 (or 128 or 127.5) from each I and Q, giving you
// a range from -127 to +128 (or -128 to +127, or -127.5 to +127.5)..
//
// To decode the AM signal, you need the magnitude of the waveform, which is given by sqrt((I^2)+(Q^2))
// The most this could be is if I&Q are both 128 (or 127 or 127.5), so you could end up with a magnitude
// of 181.019 (or 179.605, or 180.312)
//
// However, in reality the magnitude of the signal should never exceed the range -1 to +1, because the
// values are I = rCos(w) and Q = rSin(w). Therefore the integer computed magnitude should (can?) never
// exceed 128 (or 127, or 127.5 or whatever)
//
// If we scale up the results so that they range from 0 to 65535 (16 bits) then we need to multiply
// by 511.99, (or 516.02 or 514). antirez's original code multiplies by 360, presumably because he's
// assuming the maximim calculated amplitude is 181.019, and (181.019 * 360) = 65166.
//
// So lets see if we can improve things by subtracting 127.5, Well in integer arithmatic we can't
// subtract half, so, we'll double everything up and subtract one, and then compensate for the doubling
// in the multiplier at the end.
//
// If we do this we can never have I or Q equal to 0 - they can only be as small as +/- 1.
// This gives us a minimum magnitude of root 2 (0.707), so the dynamic range becomes (1.414-255). This
// also affects our scaling value, which is now 65535/(255 - 1.414), or 258.433254
//
// The sums then become mag = 258.433254 * (sqrt((I*2-255)^2 + (Q*2-255)^2) - 1.414)
// or mag = (258.433254 * sqrt((I*2-255)^2 + (Q*2-255)^2)) - 365.4798
//
// We also need to clip mag just incaes any rogue I/Q values somehow do have a magnitude greater than 255.
//
for (i = 0; i <= 255; i++) {
for (q = 0; q <= 255; q++) {
int mag, mag_i, mag_q;
mag_i = (i * 2) - 255;
mag_q = (q * 2) - 255;
mag = (int) round((sqrt((mag_i*mag_i)+(mag_q*mag_q)) * 258.433254) - 365.4798);
Modes.maglut[(i*256)+q] = (uint16_t) ((mag < 65535) ? mag : 65535);
}
}
/* Prepare error correction tables */
modesInitErrorInfo();
}
/* =============================== RTLSDR handling ========================== */
void modesInitRTLSDR(void) {
int j;
int device_count;
char vendor[256], product[256], serial[256];
device_count = rtlsdr_get_device_count();
if (!device_count) {
fprintf(stderr, "No supported RTLSDR devices found.\n");
exit(1);
}
fprintf(stderr, "Found %d device(s):\n", device_count);
for (j = 0; j < device_count; j++) {
rtlsdr_get_device_usb_strings(j, vendor, product, serial);
fprintf(stderr, "%d: %s, %s, SN: %s %s\n", j, vendor, product, serial,
(j == Modes.dev_index) ? "(currently selected)" : "");
}
if (rtlsdr_open(&Modes.dev, Modes.dev_index) < 0) {
fprintf(stderr, "Error opening the RTLSDR device: %s\n",
strerror(errno));
exit(1);
}
/* Set gain, frequency, sample rate, and reset the device. */
rtlsdr_set_tuner_gain_mode(Modes.dev,
(Modes.gain == MODES_AUTO_GAIN) ? 0 : 1);
if (Modes.gain != MODES_AUTO_GAIN) {
if (Modes.gain == MODES_MAX_GAIN) {
/* Find the maximum gain available. */
int numgains;
int gains[100];
numgains = rtlsdr_get_tuner_gains(Modes.dev, gains);
Modes.gain = gains[numgains-1];
fprintf(stderr, "Max available gain is: %.2f\n", Modes.gain/10.0);
}
rtlsdr_set_tuner_gain(Modes.dev, Modes.gain);
fprintf(stderr, "Setting gain to: %.2f\n", Modes.gain/10.0);
} else {
fprintf(stderr, "Using automatic gain control.\n");
}
rtlsdr_set_freq_correction(Modes.dev, Modes.ppm_error);
if (Modes.enable_agc) rtlsdr_set_agc_mode(Modes.dev, 1);
rtlsdr_set_center_freq(Modes.dev, Modes.freq);
rtlsdr_set_sample_rate(Modes.dev, MODES_DEFAULT_RATE);
rtlsdr_reset_buffer(Modes.dev);
fprintf(stderr, "Gain reported by device: %.2f\n",
rtlsdr_get_tuner_gain(Modes.dev)/10.0);
}
/* We use a thread reading data in background, while the main thread
* handles decoding and visualization of data to the user.
*
* The reading thread calls the RTLSDR API to read data asynchronously, and
* uses a callback to populate the data buffer.
* A Mutex is used to avoid races with the decoding thread. */
void rtlsdrCallback(unsigned char *buf, uint32_t len, void *ctx) {
MODES_NOTUSED(ctx);
pthread_mutex_lock(&Modes.data_mutex);
ftime(&Modes.stSystemTimeRTL);
if (len > MODES_ASYNC_BUF_SIZE) len = MODES_ASYNC_BUF_SIZE;
/* Read the new data. */
memcpy(Modes.data, buf, len);
Modes.data_ready = 1;
/* Signal to the other thread that new data is ready */
pthread_cond_signal(&Modes.data_cond);
pthread_mutex_unlock(&Modes.data_mutex);
}
/* This is used when --ifile is specified in order to read data from file
* instead of using an RTLSDR device. */
void readDataFromFile(void) {
pthread_mutex_lock(&Modes.data_mutex);
while(1) {
ssize_t nread, toread;
unsigned char *p;
if (Modes.data_ready) {
pthread_cond_wait(&Modes.data_cond,&Modes.data_mutex);
continue;
}
if (Modes.interactive) {
/* When --ifile and --interactive are used together, slow down
* playing at the natural rate of the RTLSDR received. */
pthread_mutex_unlock(&Modes.data_mutex);
usleep(64000);
pthread_mutex_lock(&Modes.data_mutex);
}
toread = MODES_ASYNC_BUF_SIZE;
p = (unsigned char *) Modes.data;
while(toread) {
nread = read(Modes.fd, p, toread);
if (nread <= 0) {
Modes.exit = 1; /* Signal the other thread to exit. */
break;
}
p += nread;
toread -= nread;
}
if (toread) {
/* Not enough data on file to fill the buffer? Pad with
* no signal. */
memset(p,127,toread);
}
Modes.data_ready = 1;
/* Signal to the other thread that new data is ready */
pthread_cond_signal(&Modes.data_cond);
}
}
/* We read data using a thread, so the main thread only handles decoding
* without caring about data acquisition. */
void *readerThreadEntryPoint(void *arg) {
MODES_NOTUSED(arg);
if (Modes.filename == NULL) {
rtlsdr_read_async(Modes.dev, rtlsdrCallback, NULL,
MODES_ASYNC_BUF_NUMBER,
MODES_ASYNC_BUF_SIZE);
} else {
readDataFromFile();
}
return NULL;
}
/* ============================== Debugging ================================= */
/* Helper function for dumpMagnitudeVector().
* It prints a single bar used to display raw signals.
*
* Since every magnitude sample is between 0-255, the function uses
* up to 63 characters for every bar. Every character represents
* a length of 4, 3, 2, 1, specifically:
*
* "O" is 4
* "o" is 3
* "-" is 2
* "." is 1
*/
void dumpMagnitudeBar(int index, int magnitude) {
char *set = " .-o";
char buf[256];
int div = magnitude / 256 / 4;
int rem = magnitude / 256 % 4;
memset(buf,'O',div);
buf[div] = set[rem];
buf[div+1] = '\0';
if (index >= 0)
printf("[%.3d] |%-66s %d\n", index, buf, magnitude);
else
printf("[%.2d] |%-66s %d\n", index, buf, magnitude);
}
/* Display an ASCII-art alike graphical representation of the undecoded
* message as a magnitude signal.
*
* The message starts at the specified offset in the "m" buffer.
* The function will display enough data to cover a short 56 bit message.
*
* If possible a few samples before the start of the messsage are included
* for context. */
void dumpMagnitudeVector(uint16_t *m, uint32_t offset) {
uint32_t padding = 5; /* Show a few samples before the actual start. */
uint32_t start = (offset < padding) ? 0 : offset-padding;
uint32_t end = offset + (MODES_PREAMBLE_SAMPLES)+(MODES_SHORT_MSG_SAMPLES) - 1;
uint32_t j;
for (j = start; j <= end; j++) {
dumpMagnitudeBar(j-offset, m[j]);
}
}
/* Produce a raw representation of the message as a Javascript file
* loadable by debug.html. */
void dumpRawMessageJS(char *descr, unsigned char *msg,
uint16_t *m, uint32_t offset, int fixable)
{
int padding = 5; /* Show a few samples before the actual start. */
int start = offset - padding;
int end = offset + (MODES_PREAMBLE_SAMPLES)+(MODES_LONG_MSG_SAMPLES) - 1;
FILE *fp;
int j;
if ((fp = fopen("frames.js","a")) == NULL) {
fprintf(stderr, "Error opening frames.js: %s\n", strerror(errno));
exit(1);
}
fprintf(fp,"frames.push({\"descr\": \"%s\", \"mag\": [", descr);
for (j = start; j <= end; j++) {
fprintf(fp,"%d", j < 0 ? 0 : m[j]);
if (j != end) fprintf(fp,",");
}
fprintf(fp,"], \"fixed\": %d, \"bits\": %d, \"hex\": \"",
fixable, modesMessageLenByType(msg[0]>>3));
for (j = 0; j < MODES_LONG_MSG_BYTES; j++)
fprintf(fp,"\\x%02x",msg[j]);
fprintf(fp,"\"});\n");
fclose(fp);
}
/* This is a wrapper for dumpMagnitudeVector() that also show the message
* in hex format with an additional description.
*
* descr is the additional message to show to describe the dump.
* msg points to the decoded message
* m is the original magnitude vector
* offset is the offset where the message starts
*
* The function also produces the Javascript file used by debug.html to
* display packets in a graphical format if the Javascript output was
* enabled.
*/
void dumpRawMessage(char *descr, unsigned char *msg,
uint16_t *m, uint32_t offset)
{
int j;
int msgtype = msg[0] >> 3;
int fixable = 0;
if (msgtype == 17) {
fixable = fixBitErrors(msg, MODES_LONG_MSG_BITS);
}
if (Modes.debug & MODES_DEBUG_JS) {
dumpRawMessageJS(descr, msg, m, offset, fixable);
return;
}
printf("\n--- %s\n ", descr);
for (j = 0; j < MODES_LONG_MSG_BYTES; j++) {
printf("%02x",msg[j]);
if (j == MODES_SHORT_MSG_BYTES-1) printf(" ... ");
}
printf(" (DF %d, Fixable: %d)\n", msgtype, fixable);
dumpMagnitudeVector(m,offset);
printf("---\n\n");
}
/* ===================== Mode A/C detection and decoding =================== */
//
// This table is used to build the Mode A/C variable called ModeABits.Each
// bit period is inspected, and if it's value exceeds the threshold limit,
// then the value in this table is or-ed into ModeABits.
//
// At the end of message processing, ModeABits will be the decoded ModeA value.
//
// We can also flag noise in bits that should be zeros - the xx bits. Noise in
// these bits cause bits (31-16) in ModeABits to be set. Then at the end of message
// processing we can test for errors by looking at these bits.
//
uint32_t ModeABitTable[24] = {
0x00000000, // F1 = 1
0x00000010, // C1
0x00001000, // A1
0x00000020, // C2
0x00002000, // A2
0x00000040, // C4
0x00004000, // A4
0x40000000, // xx = 0 Set bit 30 if we see this high
0x00000100, // B1
0x00000001, // D1
0x00000200, // B2
0x00000002, // D2
0x00000400, // B4
0x00000004, // D4
0x00000000, // F2 = 1
0x08000000, // xx = 0 Set bit 27 if we see this high
0x04000000, // xx = 0 Set bit 26 if we see this high
0x00000080, // SPI
0x02000000, // xx = 0 Set bit 25 if we see this high
0x01000000, // xx = 0 Set bit 24 if we see this high
0x00800000, // xx = 0 Set bit 23 if we see this high
0x00400000, // xx = 0 Set bit 22 if we see this high
0x00200000, // xx = 0 Set bit 21 if we see this high
0x00100000, // xx = 0 Set bit 20 if we see this high
};
//
// This table is used to produce an error variable called ModeAErrs.Each
// inter-bit period is inspected, and if it's value falls outside of the
// expected range, then the value in this table is or-ed into ModeAErrs.
//
// At the end of message processing, ModeAErrs will indicate if we saw
// any inter-bit anomolies, and the bits that are set will show which
// bits had them.
//
uint32_t ModeAMidTable[24] = {
0x80000000, // F1 = 1 Set bit 31 if we see F1_C1 error
0x00000010, // C1 Set bit 4 if we see C1_A1 error
0x00001000, // A1 Set bit 12 if we see A1_C2 error
0x00000020, // C2 Set bit 5 if we see C2_A2 error
0x00002000, // A2 Set bit 13 if we see A2_C4 error
0x00000040, // C4 Set bit 6 if we see C3_A4 error
0x00004000, // A4 Set bit 14 if we see A4_xx error
0x40000000, // xx = 0 Set bit 30 if we see xx_B1 error
0x00000100, // B1 Set bit 8 if we see B1_D1 error
0x00000001, // D1 Set bit 0 if we see D1_B2 error
0x00000200, // B2 Set bit 9 if we see B2_D2 error
0x00000002, // D2 Set bit 1 if we see D2_B4 error
0x00000400, // B4 Set bit 10 if we see B4_D4 error
0x00000004, // D4 Set bit 2 if we see D4_F2 error
0x20000000, // F2 = 1 Set bit 29 if we see F2_xx error
0x08000000, // xx = 0 Set bit 27 if we see xx_xx error
0x04000000, // xx = 0 Set bit 26 if we see xx_SPI error
0x00000080, // SPI Set bit 15 if we see SPI_xx error
0x02000000, // xx = 0 Set bit 25 if we see xx_xx error
0x01000000, // xx = 0 Set bit 24 if we see xx_xx error
0x00800000, // xx = 0 Set bit 23 if we see xx_xx error
0x00400000, // xx = 0 Set bit 22 if we see xx_xx error
0x00200000, // xx = 0 Set bit 21 if we see xx_xx error
0x00100000, // xx = 0 Set bit 20 if we see xx_xx error
};
//
// The "off air" format is,,
// _F1_C1_A1_C2_A2_C4_A4_xx_B1_D1_B2_D2_B4_D4_F2_xx_xx_SPI_
//
// Bit spacing is 1.45uS, with 0.45uS high, and 1.00us low. This is a problem
// because we ase sampling at 2Mhz (500nS) so we are below Nyquist.
//
// The bit spacings are..
// F1 : 0.00,
// 1.45, 2.90, 4.35, 5.80, 7.25, 8.70,
// X : 10.15,
// : 11.60, 13.05, 14.50, 15.95, 17.40, 18.85,
// F2 : 20.30,
// X : 21.75, 23.20, 24.65
//
// This equates to the following sample point centers at 2Mhz.
// [ 0.0],
// [ 2.9], [ 5.8], [ 8.7], [11.6], [14.5], [17.4],
// [20.3],
// [23.2], [26.1], [29.0], [31.9], [34.8], [37.7]
// [40.6]
// [43.5], [46.4], [49.3]
//
// We know that this is a supposed to be a binary stream, so the signal
// should either be a 1 or a 0. Therefore, any energy above the noise level
// in two adjacent samples must be from the same pulse, so we can simply
// add the values together..
//
int detectModeA(uint16_t *m, struct modesMessage *mm)
{
int j, lastBitWasOne;
int ModeABits = 0;
int ModeAErrs = 0;
int byte, bit;
int thisSample, lastBit, lastSpace = 0;
int m0, m1, m2, m3, mPhase;
int n0, n1, n2 ,n3;
int F1_sig, F1_noise;
int F2_sig, F2_noise;
int fSig, fNoise, fLevel, fLoLo;
// m[0] contains the energy from 0 -> 499 nS
// m[1] contains the energy from 500 -> 999 nS
// m[2] contains the energy from 1000 -> 1499 nS
// m[3] contains the energy from 1500 -> 1999 nS
//
// We are looking for a Frame bit (F1) whose width is 450nS, followed by
// 1000nS of quiet.
//
// The width of the frame bit is 450nS, which is 90% of our sample rate.
// Therefore, in an ideal world, all the energy for the frame bit will be
// in a single sample, preceeded by (at least) one zero, and followed by
// two zeros, Best case we can look for ...
//
// 0 - 1 - 0 - 0
//
// However, our samples are not phase aligned, so some of the energy from
// each bit could be spread over two consecutive samples. Worst case is
// that we sample half in one bit, and half in the next. In that case,
// we're looking for
//
// 0 - 0.5 - 0.5 - 0.
m0 = m[0]; m1 = m[1];
if (m0 >= m1) // m1 *must* be bigger than m0 for this to be F1
{return (0);}
m2 = m[2]; m3 = m[3];
//
// if (m2 <= m0), then assume the sample bob on (Phase == 0), so don't look at m3
if ((m2 <= m0) || (m2 < m3))
{m3 = m2; m2 = m0;}
if ( (m3 >= m1) // m1 must be bigger than m3
|| (m0 > m2) // m2 can be equal to m0 if ( 0,1,0,0 )
|| (m3 > m2) ) // m2 can be equal to m3 if ( 0,1,0,0 )
{return (0);}
// m0 = noise
// m1 = noise + (signal * X))
// m2 = noise + (signal * (1-X))
// m3 = noise
//
// Hence, assuming all 4 samples have similar amounts of noise in them
// signal = (m1 + m2) - ((m0 + m3) * 2)
// noise = (m0 + m3) / 2
//
F1_sig = (m1 + m2) - ((m0 + m3) << 1);
F1_noise = (m0 + m3) >> 1;
if ( (F1_sig < MODEAC_MSG_SQUELCH_LEVEL) // minimum required F1 signal amplitude
|| (F1_sig < (F1_noise << 2)) ) // minimum allowable Sig/Noise ratio 4:1
{return (0);}
// If we get here then we have a potential F1, so look for an equally valid F2 20.3uS later
//
// Our F1 is centered somewhere between samples m[1] and m[2]. We can guestimate where F2 is
// by comparing the ratio of m1 and m2, and adding on 20.3 uS (40.6 samples)
//
mPhase = ((m2 * 20) / (m1 + m2));
byte = (mPhase + 812) / 20;
n0 = m[byte++]; n1 = m[byte++];
if (n0 >= n1) // n1 *must* be bigger than n0 for this to be F2
{return (0);}
n2 = m[byte++];
//
// if the sample bob on (Phase == 0), don't look at n3
//
if ((mPhase + 812) % 20)
{n3 = m[byte++];}
else
{n3 = n2; n2 = n0;}
if ( (n3 >= n1) // n1 must be bigger than n3
|| (n0 > n2) // n2 can be equal to n0 ( 0,1,0,0 )
|| (n3 > n2) ) // n2 can be equal to n3 ( 0,1,0,0 )
{return (0);}
F2_sig = (n1 + n2) - ((n0 + n3) << 1);
F2_noise = (n0 + n3) >> 1;
if ( (F2_sig < MODEAC_MSG_SQUELCH_LEVEL) // minimum required F2 signal amplitude
|| (F2_sig < (F2_noise << 2)) ) // maximum allowable Sig/Noise ratio 4:1
{return (0);}
fSig = (F1_sig + F2_sig) >> 1;
fNoise = (F1_noise + F2_noise) >> 1;
fLoLo = fNoise + (fSig >> 2); // 1/2
fLevel = fNoise + (fSig >> 1);
lastBitWasOne = 1;
lastBit = F1_sig;
//
// Now step by a half ModeA bit, 0.725nS, which is 1.45 samples, which is 29/20
// No need to do bit 0 because we've already selected it as a valid F1
// Do several bits past the SPI to increase error rejection
//
for (j = 1, mPhase += 29; j < 48; mPhase += 29, j ++)
{
byte = 1 + (mPhase / 20);
thisSample = m[byte] - fNoise;
if (mPhase % 20) // If the bit is split over two samples...
{thisSample += (m[byte+1] - fNoise);} // add in the second sample's energy
// If we're calculating a space value
if (j & 1)
{lastSpace = thisSample;}
else
{// We're calculating a new bit value
bit = j >> 1;
if (thisSample >= fLevel)
{// We're calculating a new bit value, and its a one
ModeABits |= ModeABitTable[bit--]; // or in the correct bit
if (lastBitWasOne)
{ // This bit is one, last bit was one, so check the last space is somewhere less than one
if ( (lastSpace >= (thisSample>>1)) || (lastSpace >= lastBit) )
{ModeAErrs |= ModeAMidTable[bit];}
}
else
{// This bit,is one, last bit was zero, so check the last space is somewhere less than one
if (lastSpace >= (thisSample >> 1))
{ModeAErrs |= ModeAMidTable[bit];}
}
lastBitWasOne = 1;
}
else
{// We're calculating a new bit value, and its a zero
if (lastBitWasOne)
{ // This bit is zero, last bit was one, so check the last space is somewhere in between
if (lastSpace >= lastBit)
{ModeAErrs |= ModeAMidTable[bit];}
}
else
{// This bit,is zero, last bit was zero, so check the last space is zero too
if (lastSpace >= fLoLo)
{ModeAErrs |= ModeAMidTable[bit];}
}
lastBitWasOne = 0;
}
lastBit = (thisSample >> 1);
}
}
//
// Output format is : 00:A4:A2:A1:00:B4:B2:B1:00:C4:C2:C1:00:D4:D2:D1
//
if ((ModeABits < 3) || (ModeABits & 0xFFFF8808) || (ModeAErrs) )
{return (ModeABits = 0);}
memset(mm, 0, sizeof(*mm));
fSig = (fSig + 0x7F) >> 8;
mm->signalLevel = ((fSig < 255) ? fSig : 255);
return ModeABits;
}
// Input format is : 00:A4:A2:A1:00:B4:B2:B1:00:C4:C2:C1:00:D4:D2:D1
int ModeAToModeC(unsigned int ModeA)
{
unsigned int FiveHundreds = 0;
unsigned int OneHundreds = 0;
if ( (ModeA & 0xFFFF888B) // D1 set is illegal. D2 set is > 62700ft which is unlikely
|| ((ModeA & 0x000000F0) == 0) ) // C1,,C4 cannot be Zero
{return -9999;}
if (ModeA & 0x0010) {OneHundreds ^= 0x007;} // C1
if (ModeA & 0x0020) {OneHundreds ^= 0x003;} // C2
if (ModeA & 0x0040) {OneHundreds ^= 0x001;} // C4
// Remove 7s from OneHundreds (Make 7->5, snd 5->7).
if ((OneHundreds & 5) == 5) {OneHundreds ^= 2;}
// Check for invalid codes, only 1 to 5 are valid
if (OneHundreds > 5)
{return -9999;}
//if (ModeA & 0x0001) {FiveHundreds ^= 0x1FF;} // D1 never used for altitude
if (ModeA & 0x0002) {FiveHundreds ^= 0x0FF;} // D2
if (ModeA & 0x0004) {FiveHundreds ^= 0x07F;} // D4
if (ModeA & 0x1000) {FiveHundreds ^= 0x03F;} // A1
if (ModeA & 0x2000) {FiveHundreds ^= 0x01F;} // A2
if (ModeA & 0x4000) {FiveHundreds ^= 0x00F;} // A4
if (ModeA & 0x0100) {FiveHundreds ^= 0x007;} // B1
if (ModeA & 0x0200) {FiveHundreds ^= 0x003;} // B2
if (ModeA & 0x0400) {FiveHundreds ^= 0x001;} // B4
// Correct order of OneHundreds.
if (FiveHundreds & 1) {OneHundreds = 6 - OneHundreds;}
return ((FiveHundreds * 5) + OneHundreds - 13);
}
void decodeModeAMessage(struct modesMessage *mm, int ModeA)
{
mm->msgtype = 32; // Valid Mode S DF's are DF-00 to DF-31.
// so use 32 to indicate Mode A/C
mm->msgbits = 16; // Fudge up a Mode S style data stream
mm->msg[0] = (ModeA >> 8);
mm->msg[1] = (ModeA);
// Fudge an ICAO address based on Mode A (remove the Ident bit)
// Use an upper address byte of FF, since this is ICAO unallocated
mm->addr = 0x00FF0000 | (ModeA & 0x0000FF7F);
// Set the Identity field to ModeA
mm->modeA = ModeA & 0x7777;
mm->bFlags |= MODES_ACFLAGS_SQUAWK_VALID;
// Flag ident in flight status
mm->fs = ModeA & 0x0080;
// Not much else we can tell from a Mode A/C reply.
// Just fudge up a few bits to keep other code happy
mm->crcok = 1;
mm->correctedbits = 0;
}
/* ===================== Mode S detection and decoding ===================== */
/* Parity table for MODE S Messages.
* The table contains 112 elements, every element corresponds to a bit set
* in the message, starting from the first bit of actual data after the
* preamble.
*
* For messages of 112 bit, the whole table is used.
* For messages of 56 bits only the last 56 elements are used.
*
* The algorithm is as simple as xoring all the elements in this table
* for which the corresponding bit on the message is set to 1.
*
* The latest 24 elements in this table are set to 0 as the checksum at the
* end of the message should not affect the computation.
*
* Note: this function can be used with DF11 and DF17, other modes have
* the CRC xored with the sender address as they are reply to interrogations,
* but a casual listener can't split the address from the checksum.
*/
uint32_t modes_checksum_table[112] = {
0x3935ea, 0x1c9af5, 0xf1b77e, 0x78dbbf, 0xc397db, 0x9e31e9, 0xb0e2f0, 0x587178,
0x2c38bc, 0x161c5e, 0x0b0e2f, 0xfa7d13, 0x82c48d, 0xbe9842, 0x5f4c21, 0xd05c14,
0x682e0a, 0x341705, 0xe5f186, 0x72f8c3, 0xc68665, 0x9cb936, 0x4e5c9b, 0xd8d449,
0x939020, 0x49c810, 0x24e408, 0x127204, 0x093902, 0x049c81, 0xfdb444, 0x7eda22,
0x3f6d11, 0xe04c8c, 0x702646, 0x381323, 0xe3f395, 0x8e03ce, 0x4701e7, 0xdc7af7,
0x91c77f, 0xb719bb, 0xa476d9, 0xadc168, 0x56e0b4, 0x2b705a, 0x15b82d, 0xf52612,
0x7a9309, 0xc2b380, 0x6159c0, 0x30ace0, 0x185670, 0x0c2b38, 0x06159c, 0x030ace,
0x018567, 0xff38b7, 0x80665f, 0xbfc92b, 0xa01e91, 0xaff54c, 0x57faa6, 0x2bfd53,
0xea04ad, 0x8af852, 0x457c29, 0xdd4410, 0x6ea208, 0x375104, 0x1ba882, 0x0dd441,
0xf91024, 0x7c8812, 0x3e4409, 0xe0d800, 0x706c00, 0x383600, 0x1c1b00, 0x0e0d80,
0x0706c0, 0x038360, 0x01c1b0, 0x00e0d8, 0x00706c, 0x003836, 0x001c1b, 0xfff409,
0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000,
0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000,
0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000, 0x000000
};
uint32_t modesChecksum(unsigned char *msg, int bits) {
uint32_t crc = 0;
uint32_t rem = 0;
int offset = (bits == 112) ? 0 : (112-56);
uint8_t theByte = *msg;
uint32_t * pCRCTable = &modes_checksum_table[offset];
int j;
for(j = 0; j < bits; j++) {
if ((j & 7) == 0)
{theByte = *msg++; rem = (rem << 8) | theByte;}
// If bit is set, xor with corresponding table entry.
if (theByte & 0x80) {crc ^= *pCRCTable;}
pCRCTable++;
theByte = theByte << 1;
}
return ((crc ^ rem) & 0x00FFFFFF); // 24 bit checksum.
}
//
// Given the Downlink Format (DF) of the message, return the message length in bits.
//
// All known DF's 16 or greater are long. All known DF's 15 or less are short.
// There are lots of unused codes in both category, so we can assume ICAO will stick to
// these rules, meaning that the most significant bit of the DF indicates the length.
//
int modesMessageLenByType(int type) {
return (type & 0x10) ? MODES_LONG_MSG_BITS : MODES_SHORT_MSG_BITS ;
}
//
// Try to fix single bit errors using the checksum. On success modifies
// the original buffer with the fixed version, and returns the position
// of the error bit. Otherwise if fixing failed -1 is returned.
//
int fixSingleBitErrors(unsigned char *msg, int bits) {
int j;
unsigned char aux[MODES_LONG_MSG_BYTES];
memcpy(aux, msg, bits/8);
// Do not attempt to error correct Bits 0-4. These contain the DF, and must
// be correct because we can only error correct DF17
for (j = 5; j < bits; j++) {
int byte = j/8;
int bitmask = 1 << (7 - (j & 7));
aux[byte] ^= bitmask; // Flip j-th bit
if (0 == modesChecksum(aux, bits)) {
// The error is fixed. Overwrite the original buffer with the
// corrected sequence, and returns the error bit position
msg[byte] = aux[byte];
return (j);
}
aux[byte] ^= bitmask; // Flip j-th bit back again
}
return (-1);
}
//
// Similar to fixSingleBitErrors() but try every possible two bit combination.
// This is very slow and should be tried only against DF17 messages that
// don't pass the checksum, and only in Aggressive Mode.
//
int fixTwoBitsErrors(unsigned char *msg, int bits) {
int j, i;
unsigned char aux[MODES_LONG_MSG_BYTES];
memcpy(aux, msg, bits/8);
// Do not attempt to error correct Bits 0-4. These contain the DF, and must
// be correct because we can only error correct DF17
for (j = 5; j < bits; j++) {
int byte1 = j/8;
int bitmask1 = 1 << (7 - (j & 7));
aux[byte1] ^= bitmask1; // Flip j-th bit
// Don't check the same pairs multiple times, so i starts from j+1
for (i = j+1; i < bits; i++) {
int byte2 = i/8;
int bitmask2 = 1 << (7 - (i & 7));
aux[byte2] ^= bitmask2; // Flip i-th bit
if (0 == modesChecksum(aux, bits)) {
// The error is fixed. Overwrite the original buffer with
// the corrected sequence, and returns the error bit position
msg[byte1] = aux[byte1];
msg[byte2] = aux[byte2];
// We return the two bits as a 16 bit integer by shifting
// 'i' on the left. This is possible since 'i' will always
// be non-zero because i starts from j+1
return (j | (i << 8));
aux[byte2] ^= bitmask2; // Flip i-th bit back
}
aux[byte1] ^= bitmask1; // Flip j-th bit back
}
}
return (-1);
}
/* Code for introducing a less CPU-intensive method of correcting
* single bit errors.
*
* Makes use of the fact that the crc checksum is linear with respect to
* the bitwise xor operation, i.e.
* crc(m^e) = (crc(m)^crc(e)
* where m and e are the message resp. error bit vectors.
*
* Call crc(e) the syndrome.
*
* The code below works by precomputing a table of (crc(e), e) for all
* possible error vectors e (here only single bit and double bit errors),
* search for the syndrome in the table, and correct the then known error.
* The error vector e is represented by one or two bit positions that are
* changed. If a second bit position is not used, it is -1.
*
* Run-time is binary search in a sorted table, plus some constant overhead,
* instead of running through all possible bit positions (resp. pairs of
* bit positions).
*
*
*
*/
struct errorinfo {
uint32_t syndrome; /* CRC syndrome */
int pos0; /* bit position of first error */
int pos1; /* bit position of second error, or -1 */
};
#define NERRORINFO \
(MODES_LONG_MSG_BITS+MODES_LONG_MSG_BITS*(MODES_LONG_MSG_BITS-1)/2)
struct errorinfo bitErrorTable[NERRORINFO];
/* Compare function as needed for stdlib's qsort and bsearch functions */
int cmpErrorInfo(const void *p0, const void *p1) {
struct errorinfo *e0 = (struct errorinfo*)p0;
struct errorinfo *e1 = (struct errorinfo*)p1;
if (e0->syndrome == e1->syndrome) {
return 0;
} else if (e0->syndrome < e1->syndrome) {
return -1;
} else {
return 1;
}
}
/* Compute the table of all syndromes for 1-bit and 2-bit error vectors */
void modesInitErrorInfo() {
unsigned char msg[MODES_LONG_MSG_BYTES];
int i, j, n;
uint32_t crc;
n = 0;
memset(bitErrorTable, 0, sizeof(bitErrorTable));
/* First, insert infos about all possible single bit errors */
for (i = 0; i < MODES_LONG_MSG_BITS; i++) {
int bytepos = (i >> 3);
int mask = 1 << (7 - (i & 7));
memset(msg, 0, MODES_LONG_MSG_BYTES);
msg[bytepos] ^= mask;
crc = modesChecksum(msg, MODES_LONG_MSG_BITS);
bitErrorTable[n].syndrome = crc;
bitErrorTable[n].pos0 = i;
bitErrorTable[n].pos1 = -1;
n += 1;
}
/* Add also all double bit errors */
for (i = 0; i < MODES_LONG_MSG_BITS; i++) {
int bytepos0 = (i >> 3);
int mask0 = 1 << (7 - (i & 7));
memset(msg, 0, MODES_LONG_MSG_BYTES);
msg[bytepos0] ^= mask0;
for (j = i+1; j < MODES_LONG_MSG_BITS; j++) {
int bytepos1 = (j >> 3);
int mask1 = 1 << (7 - (j & 7));
msg[bytepos1] ^= mask1;
crc = modesChecksum(msg, MODES_LONG_MSG_BITS);
if (n >= NERRORINFO) {
/*
fprintf(stderr,
"Internal error, too many "
"entries, fix NERRORINFO\n");
*/
break;
}
bitErrorTable[n].syndrome = crc;
bitErrorTable[n].pos0 = i;
bitErrorTable[n].pos1 = j;
n += 1;
}
}
qsort(bitErrorTable, NERRORINFO,
sizeof(struct errorinfo), cmpErrorInfo);
/* Test code: report if any syndrome appears at least twice. In this
* case the correction cannot be done without ambiguity.
* Tried it, does not happen for 1- and 2-bit errors.
*/
/*
for (i = 1; i < NERRORINFO; i++) {
if (bitErrorTable[i-1].syndrome
== bitErrorTable[i].syndrome) {
fprintf(stderr, "modesInitErrorInfo: "
"Collision for syndrome %06x\n",
(int)bitErrorTable[i].syndrome);
}
}
*/
/*
for (i = 0; i < NERRORINFO; i++) {
printf("syndrome %06x bit0 %3d bit1 %3d\n",
bitErrorTable[i].syndrome,
bitErrorTable[i].pos0, bitErrorTable[i].pos1);
}
*/
}
/* Flip a bit, but make sure that the DF field (first 5 bits)
* is never changed
*/
int flipBit(unsigned char *msg, int nbits, int bit) {
int bytepos, mask;
if ((bit < 0) || (bit >= nbits)) {
return 0;
}
if (bit < 5) {
return 0;
}
bytepos = (bit >> 3);
mask = 1 << (7 - (bit & 7));
msg[bytepos] ^= mask;
return 1;
}
/* Search syndrome in table and, if an entry is found, flip the necessary
* bits. Make sure the indices fit into the array, and for 2-bit errors,
* are different.
* Return number of fixed bits.
*/
int fixBitErrors(unsigned char *msg, int bits) {
struct errorinfo *pei;
struct errorinfo ei;
int bitpos0, bitpos1, offset, res;
ei.syndrome = modesChecksum(msg, bits);
ei.pos0 = -1;
ei.pos1 = -1;
pei = bsearch(&ei, bitErrorTable, NERRORINFO,
sizeof(struct errorinfo), cmpErrorInfo);
if (pei == NULL) {
/* Nothing found */
return 0;
}
offset = MODES_LONG_MSG_BITS-bits;
bitpos0 = pei->pos0;
bitpos1 = pei->pos1;
res = 0;
if (bitpos1 >= 0) { /* two-bit error pattern */
bitpos0 -= offset;
bitpos1 -= offset;
if ((bitpos0 < 0) || (bitpos0 >= bits) ||
(bitpos1 < 0) || (bitpos1 >= bits)) {
return res;
}
res +=flipBit(msg, bits, bitpos0);
if (bitpos0 != bitpos1) {
res += flipBit(msg, bits, bitpos1);
return res;
}
return res;
} else {
bitpos0 -= offset;
if ((bitpos0 < 0) || (bitpos0 >= bits)) {
return res;
}
res += flipBit(msg, bits, bitpos0);
return res;
}
}
/* Code for testing the timing: run all possible 1- and 2-bit error
* the test message by all 1-bit errors. Run the old code against
* all of them, and new the code.
*
* Example measurements:
* Timing old vs. new crc correction code:
* Old code: 1-bit errors on 112 msgs: 3934 usecs
* New code: 1-bit errors on 112 msgs: 104 usecs
* Old code: 2-bit errors on 6216 msgs: 407743 usecs
* New code: 2-bit errors on 6216 msgs: 5176 usecs
* indicating a 37-fold resp. 78-fold improvement in speed for 1-bit resp.
* 2-bit error.
*/
unsigned char tmsg0[MODES_LONG_MSG_BYTES] = {
/* Test data: first ADS-B message from testfiles/modes1.bin */
0x8f, 0x4d, 0x20, 0x23, 0x58, 0x7f, 0x34, 0x5e,
0x35, 0x83, 0x7e, 0x22, 0x18, 0xb2
};
#define NTWOBITS (MODES_LONG_MSG_BITS*(MODES_LONG_MSG_BITS-1)/2)
unsigned char tmsg1[MODES_LONG_MSG_BITS][MODES_LONG_MSG_BYTES];
unsigned char tmsg2[NTWOBITS][MODES_LONG_MSG_BYTES];
/* Init an array of cloned messages with all possible 1-bit errors present,
* applied to each message at the respective position
*/
void inittmsg1() {
int i, bytepos, mask;
for (i = 0; i < MODES_LONG_MSG_BITS; i++) {
bytepos = i >> 3;
mask = 1 << (7 - (i & 7));
memcpy(&tmsg1[i][0], tmsg0, MODES_LONG_MSG_BYTES);
tmsg1[i][bytepos] ^= mask;
}
}
/* Run sanity check on all but first 5 messages / bits, as those bits
* are not corrected.
*/
void checktmsg1(FILE *out) {
int i, k;
uint32_t crc;
for (i = 5; i < MODES_LONG_MSG_BITS; i++) {
crc = modesChecksum(&tmsg1[i][0], MODES_LONG_MSG_BITS);
if (crc != 0) {
fprintf(out, "CRC not fixed for "
"positon %d\n", i);
fprintf(out, " MSG ");
for (k = 0; k < MODES_LONG_MSG_BYTES; k++) {
fprintf(out, "%02x", tmsg1[i][k]);
}
fprintf(out, "\n");
}
}
}
void inittmsg2() {
int i, j, n, bytepos0, bytepos1, mask0, mask1;
n = 0;
for (i = 0; i < MODES_LONG_MSG_BITS; i++) {
bytepos0 = i >> 3;
mask0 = 1 << (7 - (i & 7));
for (j = i+1; j < MODES_LONG_MSG_BITS; j++) {
bytepos1 = j >> 3;
mask1 = 1 << (7 - (j & 7));
memcpy(&tmsg2[n][0], tmsg0, MODES_LONG_MSG_BYTES);
tmsg2[n][bytepos0] ^= mask0;
tmsg2[n][bytepos1] ^= mask1;
n += 1;
}
}
}
long difftvusec(struct timeval *t0, struct timeval *t1) {
long res = 0;
res = t1->tv_usec-t0->tv_usec;
res += (t1->tv_sec-t0->tv_sec)*1000000L;
return res;
}
/* the actual test code */
void testAndTimeBitCorrection() {
struct timeval starttv, endtv;
int i;
/* Run timing on 1-bit errors */
printf("Timing old vs. new crc correction code:\n");
inittmsg1();
gettimeofday(&starttv, NULL);
for (i = 0; i < MODES_LONG_MSG_BITS; i++) {
fixSingleBitErrors(&tmsg1[i][0], MODES_LONG_MSG_BITS);
}
gettimeofday(&endtv, NULL);
printf(" Old code: 1-bit errors on %d msgs: %ld usecs\n",
MODES_LONG_MSG_BITS, difftvusec(&starttv, &endtv));
checktmsg1(stdout);
/* Re-init */
inittmsg1();
gettimeofday(&starttv, NULL);
for (i = 0; i < MODES_LONG_MSG_BITS; i++) {
fixBitErrors(&tmsg1[i][0], MODES_LONG_MSG_BITS);
}
gettimeofday(&endtv, NULL);
printf(" New code: 1-bit errors on %d msgs: %ld usecs\n",
MODES_LONG_MSG_BITS, difftvusec(&starttv, &endtv));
checktmsg1(stdout);
/* Run timing on 2-bit errors */
inittmsg2();
gettimeofday(&starttv, NULL);
for (i = 0; i < NTWOBITS; i++) {
fixSingleBitErrors(&tmsg2[i][0], MODES_LONG_MSG_BITS);
}
gettimeofday(&endtv, NULL);
printf(" Old code: 2-bit errors on %d msgs: %ld usecs\n",
NTWOBITS, difftvusec(&starttv, &endtv));
/* Re-init */
inittmsg2();
gettimeofday(&starttv, NULL);
for (i = 0; i < NTWOBITS; i++) {
fixBitErrors(&tmsg2[i][0], MODES_LONG_MSG_BITS);
}
gettimeofday(&endtv, NULL);
printf(" New code: 2-bit errors on %d msgs: %ld usecs\n",
NTWOBITS, difftvusec(&starttv, &endtv));
}
/* Hash the ICAO address to index our cache of MODES_ICAO_CACHE_LEN
* elements, that is assumed to be a power of two. */
uint32_t ICAOCacheHashAddress(uint32_t a) {
/* The following three rounds wil make sure that every bit affects
* every output bit with ~ 50% of probability. */
a = ((a >> 16) ^ a) * 0x45d9f3b;
a = ((a >> 16) ^ a) * 0x45d9f3b;
a = ((a >> 16) ^ a);
return a & (MODES_ICAO_CACHE_LEN-1);
}
/* Add the specified entry to the cache of recently seen ICAO addresses.
* Note that we also add a timestamp so that we can make sure that the
* entry is only valid for MODES_ICAO_CACHE_TTL seconds. */
void addRecentlySeenICAOAddr(uint32_t addr) {
uint32_t h = ICAOCacheHashAddress(addr);
Modes.icao_cache[h*2] = addr;
Modes.icao_cache[h*2+1] = (uint32_t) time(NULL);
}
/* Returns 1 if the specified ICAO address was seen in a DF format with
* proper checksum (not xored with address) no more than * MODES_ICAO_CACHE_TTL
* seconds ago. Otherwise returns 0. */
int ICAOAddressWasRecentlySeen(uint32_t addr) {
uint32_t h = ICAOCacheHashAddress(addr);
uint32_t a = Modes.icao_cache[h*2];
uint32_t t = Modes.icao_cache[h*2+1];
return a && a == addr && time(NULL)-t <= MODES_ICAO_CACHE_TTL;
}
//
// In the squawk (identity) field bits are interleaved as follows in
// (message bit 20 to bit 32):
//
// C1-A1-C2-A2-C4-A4-ZERO-B1-D1-B2-D2-B4-D4
//
// So every group of three bits A, B, C, D represent an integer from 0 to 7.
//
// The actual meaning is just 4 octal numbers, but we convert it into a hex
// number tha happens to represent the four octal numbers.
//
// For more info: http://en.wikipedia.org/wiki/Gillham_code
//
int decodeID13Field(int ID13Field) {
int hexGillham = 0;
if (ID13Field & 0x1000) {hexGillham |= 0x0010;} // Bit 12 = C1
if (ID13Field & 0x0800) {hexGillham |= 0x1000;} // Bit 11 = A1
if (ID13Field & 0x0400) {hexGillham |= 0x0020;} // Bit 10 = C2
if (ID13Field & 0x0200) {hexGillham |= 0x2000;} // Bit 9 = A2
if (ID13Field & 0x0100) {hexGillham |= 0x0040;} // Bit 8 = C4
if (ID13Field & 0x0080) {hexGillham |= 0x4000;} // Bit 7 = A4
//if (ID13Field & 0x0040) {hexGillham |= 0x0800;} // Bit 6 = X or M
if (ID13Field & 0x0020) {hexGillham |= 0x0100;} // Bit 5 = B1
if (ID13Field & 0x0010) {hexGillham |= 0x0001;} // Bit 4 = D1 or Q
if (ID13Field & 0x0008) {hexGillham |= 0x0200;} // Bit 3 = B2
if (ID13Field & 0x0004) {hexGillham |= 0x0002;} // Bit 2 = D2
if (ID13Field & 0x0002) {hexGillham |= 0x0400;} // Bit 1 = B4
if (ID13Field & 0x0001) {hexGillham |= 0x0004;} // Bit 0 = D4
return (hexGillham);
}
//
// Decode the 13 bit AC altitude field (in DF 20 and others).
// Returns the altitude, and set 'unit' to either MODES_UNIT_METERS or MDOES_UNIT_FEETS.
//
int decodeAC13Field(int AC13Field, int *unit) {
int m_bit = AC13Field & 0x0040; // set = meters, clear = feet
int q_bit = AC13Field & 0x0010; // set = 25 ft encoding, clear = Gillham Mode C encoding
if (!m_bit) {
*unit = MODES_UNIT_FEET;
if (q_bit) {
// N is the 11 bit integer resulting from the removal of bit Q and M
int n = ((AC13Field & 0x1F80) >> 2) |
((AC13Field & 0x0020) >> 1) |
(AC13Field & 0x000F);
// The final altitude is resulting number multiplied by 25, minus 1000.
return ((n * 25) - 1000);
} else {
// N is an 11 bit Gillham coded altitude
int n = ModeAToModeC(decodeID13Field(AC13Field));
if (n < -12) {n = 0;}
return (100 * n);
}
} else {
*unit = MODES_UNIT_METERS;
// TODO: Implement altitude when meter unit is selected
}
return 0;
}
//
// Decode the 12 bit AC altitude field (in DF 17 and others).
//
int decodeAC12Field(int AC12Field, int *unit) {
int q_bit = AC12Field & 0x10; // Bit 48 = Q
*unit = MODES_UNIT_FEET;
if (q_bit) {
/// N is the 11 bit integer resulting from the removal of bit Q at bit 4
int n = ((AC12Field & 0x0FE0) >> 1) |
(AC12Field & 0x000F);
// The final altitude is the resulting number multiplied by 25, minus 1000.
return ((n * 25) - 1000);
} else {
// Make N a 13 bit Gillham coded altitude by inserting M=0 at bit 6
int n = ((AC12Field & 0x0FC0) << 1) |
(AC12Field & 0x003F);
n = ModeAToModeC(decodeID13Field(n));
if (n < -12) {n = 0;}
return (100 * n);
}
}
//
// Decode the 7 bit ground movement field PWL exponential style scale
//
int decodeMovementField(int movement) {
int gspeed;
// Note : movement codes 0,125,126,127 are all invalid, but they are
// trapped for before this function is called.
if (movement > 123) gspeed = 199; // > 175kt
else if (movement > 108) gspeed = ((movement - 108) * 5) + 100;
else if (movement > 93) gspeed = ((movement - 93) * 2) + 70;
else if (movement > 38) gspeed = ((movement - 38) ) + 15;
else if (movement > 12) gspeed = ((movement - 11) >> 1) + 2;
else if (movement > 8) gspeed = ((movement - 6) >> 2) + 1;
else gspeed = 0;
return (gspeed);
}
/* Capability table. */
char *ca_str[8] = {
/* 0 */ "Level 1 (Survillance Only)",
/* 1 */ "Level 2 (DF0,4,5,11)",
/* 2 */ "Level 3 (DF0,4,5,11,20,21)",
/* 3 */ "Level 4 (DF0,4,5,11,20,21,24)",
/* 4 */ "Level 2+3+4 (DF0,4,5,11,20,21,24,code7 - is on ground)",
/* 5 */ "Level 2+3+4 (DF0,4,5,11,20,21,24,code7 - is on airborne)",
/* 6 */ "Level 2+3+4 (DF0,4,5,11,20,21,24,code7)",
/* 7 */ "Level 7 ???"
};
/* Flight status table. */
char *fs_str[8] = {
/* 0 */ "Normal, Airborne",
/* 1 */ "Normal, On the ground",
/* 2 */ "ALERT, Airborne",
/* 3 */ "ALERT, On the ground",
/* 4 */ "ALERT & Special Position Identification. Airborne or Ground",
/* 5 */ "Special Position Identification. Airborne or Ground",
/* 6 */ "Value 6 is not assigned",
/* 7 */ "Value 7 is not assigned"
};
char *getMEDescription(int metype, int mesub) {
char *mename = "Unknown";
if (metype >= 1 && metype <= 4)
mename = "Aircraft Identification and Category";
else if (metype >= 5 && metype <= 8)
mename = "Surface Position";
else if (metype >= 9 && metype <= 18)
mename = "Airborne Position (Baro Altitude)";
else if (metype == 19 && mesub >=1 && mesub <= 4)
mename = "Airborne Velocity";
else if (metype >= 20 && metype <= 22)
mename = "Airborne Position (GNSS Height)";
else if (metype == 23 && mesub == 0)
mename = "Test Message";
else if (metype == 24 && mesub == 1)
mename = "Surface System Status";
else if (metype == 28 && mesub == 1)
mename = "Extended Squitter Aircraft Status (Emergency)";
else if (metype == 28 && mesub == 2)
mename = "Extended Squitter Aircraft Status (1090ES TCAS RA)";
else if (metype == 29 && (mesub == 0 || mesub == 1))
mename = "Target State and Status Message";
else if (metype == 31 && (mesub == 0 || mesub == 1))
mename = "Aircraft Operational Status Message";
return mename;
}
//
// Decode a raw Mode S message demodulated as a stream of bytes by detectModeS(),
// and split it into fields populating a modesMessage structure.
//
void decodeModesMessage(struct modesMessage *mm, unsigned char *msg) {
char *ais_charset = "?ABCDEFGHIJKLMNOPQRSTUVWXYZ????? ???????????????0123456789??????";
// Work on our local copy
memcpy(mm->msg, msg, MODES_LONG_MSG_BYTES);
msg = mm->msg;
// Get the message type ASAP as other operations depend on this
mm->msgtype = msg[0] >> 3; // Downlink Format
mm->msgbits = modesMessageLenByType(mm->msgtype);
mm->correctedbits = 0; // No errors fixed
mm->phase_corrected = 0;
mm->crc = modesChecksum(msg, mm->msgbits);
if ((mm->crc) && (Modes.fix_errors) && (mm->msgtype == 17)) {
// if ((mm->crc) && (Modes.fix_errors) && ((mm->msgtype == 11) || (mm->msgtype == 17))) {
//
// Fixing single bit errors in DF-11 is a bit dodgy because we have no way to
// know for sure if the crc is supposed to be 0 or not - it could be any value
// less than 80. Therefore, attempting to fix DF-11 errors can result in a
// multitude of possible crc solutions, only one of which is correct.
//
// We should probably perform some sanity checks on corrected DF-11's before
// using the results. Perhaps check the ICAO against known aircraft, and check
// IID against known good IID's. That's a TODO.
//
mm->correctedbits = fixBitErrors(msg, mm->msgbits);
//if ((mm->errorbit == -1) && (Modes.aggressive)) {
// mm->errorbit = fixTwoBitsErrors(msg, mm->msgbits);
//}
}
//
// Note that most of the other computation happens *after* we fix the
// single/two bit errors, otherwise we would need to recompute the fields again.
//
if (mm->msgtype == 11) { // DF 11
mm->crcok = (mm->crc < 80);
mm->iid = mm->crc;
mm->addr = (msg[1] << 16) | (msg[2] << 8) | (msg[3]);
if (0 == mm->crc) {
// DF 11 : if crc == 0 try to populate our ICAO addresses whitelist.
addRecentlySeenICAOAddr(mm->addr);
}
} else if (mm->msgtype == 17) { // DF 17
mm->crcok = (mm->crc == 0);
mm->addr = (msg[1] << 16) | (msg[2] << 8) | (msg[3]);
if (0 != mm->correctedbits) {
// DF 17 : if (error corrected) force crc = 0 but do not try to add this address
// to the whitelist of recently seen ICAO addresses.
mm->crc = 0;
} else if (0 == mm->crc) {
// DF 17 : if uncorrected and crc == 0 add this address to the whitelist of
// recently seen ICAO addresses.
addRecentlySeenICAOAddr(mm->addr);
}
} else { // All other DF's
// Compare the checksum with the whitelist of recently seen ICAO
// addresses. If it matches one, then declare the message as valid
mm->addr = mm->crc;
mm->crcok = ICAOAddressWasRecentlySeen(mm->crc);
}
// Fields for DF0, DF16
if (mm->msgtype == 0 || mm->msgtype == 16) {
if (msg[0] & 0x04) { // VS Bit
mm->bFlags |= MODES_ACFLAGS_AOG_VALID | MODES_ACFLAGS_AOG;
} else {
mm->bFlags |= MODES_ACFLAGS_AOG_VALID;
}
}
// Fields for DF11, DF17
if (mm->msgtype == 11 || mm->msgtype == 17) {
mm->ca = msg[0] & 0x07; // Responder capabilities
if (mm->ca == 4) {
mm->bFlags |= MODES_ACFLAGS_AOG_VALID | MODES_ACFLAGS_AOG;
} else if (mm->ca == 5) {
mm->bFlags |= MODES_ACFLAGS_AOG_VALID;
}
}
// Fields for DF5, DF21 = Gillham encoded Squawk
if (mm->msgtype == 5 || mm->msgtype == 21) {
int ID13Field = ((msg[2] << 8) | msg[3]) & 0x1FFF;
if (ID13Field) {
mm->bFlags |= MODES_ACFLAGS_SQUAWK_VALID;
mm->modeA = decodeID13Field(ID13Field);
}
}
// Fields for DF0, DF4, DF16, DF20 13 bit altitude
if (mm->msgtype == 0 || mm->msgtype == 4 ||
mm->msgtype == 16 || mm->msgtype == 20) {
int AC13Field = ((msg[2] << 8) | msg[3]) & 0x1FFF;
if (AC13Field) { // Only attempt to decode if a valid (non zero) altitude is present
mm->bFlags |= MODES_ACFLAGS_ALTITUDE_VALID;
mm->altitude = decodeAC13Field(AC13Field, &mm->unit);
}
}
// Fields for DF4, DF5, DF20, DF21
if ((mm->msgtype == 4) || (mm->msgtype == 20) ||
(mm->msgtype == 5) || (mm->msgtype == 21)) {
mm->bFlags |= MODES_ACFLAGS_FS_VALID;
mm->fs = msg[0] & 7; // Flight status for DF4,5,20,21
if (mm->fs <= 3) {
mm->bFlags |= MODES_ACFLAGS_AOG_VALID;
if (mm->fs & 1)
{mm->bFlags |= MODES_ACFLAGS_AOG;}
}
}
// Fields for DF17 squitter
if (mm->msgtype == 17) {
int metype = mm->metype = msg[4] >> 3; // Extended squitter message type
int mesub = mm->mesub = msg[4] & 7; // Extended squitter message subtype
// Decode the extended squitter message
if (metype >= 1 && metype <= 4) { // Aircraft Identification and Category
uint32_t chars;
mm->bFlags |= MODES_ACFLAGS_CALLSIGN_VALID;
chars = (msg[5] << 16) | (msg[6] << 8) | (msg[7]);
mm->flight[3] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[2] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[1] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[0] = ais_charset[chars & 0x3F];
chars = (msg[8] << 16) | (msg[9] << 8) | (msg[10]);
mm->flight[7] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[6] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[5] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[4] = ais_charset[chars & 0x3F];
mm->flight[8] = '\0';
} else if (metype >= 5 && metype <= 18) { // Position Message
mm->raw_latitude = ((msg[6] & 3) << 15) | (msg[7] << 7) | (msg[8] >> 1);
mm->raw_longitude = ((msg[8] & 1) << 16) | (msg[9] << 8) | (msg[10]);
mm->bFlags |= (mm->msg[6] & 0x04) ? MODES_ACFLAGS_LLODD_VALID
: MODES_ACFLAGS_LLEVEN_VALID;
if (metype >= 9) { // Airborne
int AC12Field = ((msg[5] << 4) | (msg[6] >> 4)) & 0x0FFF;
mm->bFlags |= MODES_ACFLAGS_AOG_VALID;
if (AC12Field) {// Only attempt to decode if a valid (non zero) altitude is present
mm->bFlags |= MODES_ACFLAGS_ALTITUDE_VALID;
mm->altitude = decodeAC12Field(AC12Field, &mm->unit);
}
} else { // Ground
int movement = ((msg[4] << 4) | (msg[5] >> 4)) & 0x007F;
mm->bFlags |= MODES_ACFLAGS_AOG_VALID | MODES_ACFLAGS_AOG;
if ((movement) && (movement < 125)) {
mm->bFlags |= MODES_ACFLAGS_SPEED_VALID;
mm->velocity = decodeMovementField(movement);
}
if (msg[5] & 0x08) {
mm->bFlags |= MODES_ACFLAGS_HEADING_VALID;
mm->heading = ((((msg[5] << 4) | (msg[6] >> 4)) & 0x007F) * 45) >> 4;
}
}
} else if (metype == 19) { // Airborne Velocity Message
if ( (mesub >= 1) && (mesub <= 4) ) {
int vert_rate = ((msg[8] & 0x07) << 6) | (msg[9] >> 2);
if (vert_rate) {
--vert_rate;
if (msg[8] & 0x08)
{vert_rate = 0 - vert_rate;}
mm->vert_rate = vert_rate * 64;
mm->bFlags |= MODES_ACFLAGS_VERTRATE_VALID;
}
}
if ((mesub == 1) || (mesub == 2)) {
int ew_raw = ((msg[5] & 0x03) << 8) | msg[6];
int ew_vel = ew_raw - 1;
int ns_raw = ((msg[7] & 0x7F) << 3) | (msg[8] >> 5);
int ns_vel = ns_raw - 1;
if (mesub == 2) { // If (supersonic) unit is 4 kts
ns_vel = ns_vel << 2;
ew_vel = ew_vel << 2;
}
if (ew_raw) { // Do East/West
mm->bFlags |= MODES_ACFLAGS_EWSPEED_VALID;
if (msg[5] & 0x04)
{ew_vel = 0 - ew_vel;}
mm->ew_velocity = ew_vel;
}
if (ns_raw) { // Do North/South
mm->bFlags |= MODES_ACFLAGS_NSSPEED_VALID;
if (msg[7] & 0x80)
{ns_vel = 0 - ns_vel;}
mm->ns_velocity = ns_vel;
}
if (ew_raw && ns_raw) {
// Compute velocity and angle from the two speed components
mm->bFlags |= (MODES_ACFLAGS_SPEED_VALID | MODES_ACFLAGS_HEADING_VALID | MODES_ACFLAGS_NSEWSPD_VALID);
mm->velocity = (int) sqrt((ns_vel * ns_vel) + (ew_vel * ew_vel));
if (mm->velocity) {
mm->heading = (int) (atan2(ew_vel, ns_vel) * 180.0 / M_PI);
// We don't want negative values but a 0-360 scale
if (mm->heading < 0) mm->heading += 360;
}
}
} else if (mesub == 3 || mesub == 4) {
int airspeed = ((msg[7] & 0x7f) << 3) | (msg[8] >> 5);
if (airspeed) {
mm->bFlags |= MODES_ACFLAGS_SPEED_VALID;
--airspeed;
if (mesub == 4) // If (supersonic) unit is 4 kts
{airspeed = airspeed << 2;}
mm->velocity = airspeed;
}
if (msg[5] & 0x04) {
mm->bFlags |= MODES_ACFLAGS_HEADING_VALID;
mm->heading = ((((msg[5] & 0x03) << 8) | msg[6]) * 45) >> 7;
}
}
}
}
// Fields for DF20, DF21 Comm-B
if ((mm->msgtype == 20) || (mm->msgtype == 21)){
if (msg[4] == 0x20) { // Aircraft Identification
uint32_t chars;
mm->bFlags |= MODES_ACFLAGS_CALLSIGN_VALID;
chars = (msg[5] << 16) | (msg[6] << 8) | (msg[7]);
mm->flight[3] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[2] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[1] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[0] = ais_charset[chars & 0x3F];
chars = (msg[8] << 16) | (msg[9] << 8) | (msg[10]);
mm->flight[7] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[6] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[5] = ais_charset[chars & 0x3F]; chars = chars >> 6;
mm->flight[4] = ais_charset[chars & 0x3F];
mm->flight[8] = '\0';
} else {
}
}
}
//
// This function gets a decoded Mode S Message and prints it on the screen
// in a human readable format.
//
void displayModesMessage(struct modesMessage *mm) {
int j;
unsigned char * pTimeStamp;
// Handle only addresses mode first.
if (Modes.onlyaddr) {
printf("%06x\n", mm->addr);
return; // Enough for --onlyaddr mode
}
// Show the raw message.
if (Modes.mlat) {
printf("@");
pTimeStamp = (unsigned char *) &mm->timestampMsg;
for (j=5; j>=0;j--) {
printf("%02X",pTimeStamp[j]);
}
} else
printf("*");
for (j = 0; j < mm->msgbits/8; j++) printf("%02x", mm->msg[j]);
printf(";\n");
if (Modes.raw) {
fflush(stdout); // Provide data to the reader ASAP
return; // Enough for --raw mode
}
if (mm->msgtype < 32)
printf("CRC: %06x (%s)\n", (int)mm->crc, mm->crcok ? "ok" : "wrong");
if (mm->correctedbits != 0)
printf("No. of bit errors fixed: %d\n", mm->correctedbits);
if (mm->msgtype == 0) { // DF 0
printf("DF 0: Short Air-Air Surveillance.\n");
printf(" Altitude : %d %s\n", mm->altitude,
(mm->unit == MODES_UNIT_METERS) ? "meters" : "feet");
printf(" ICAO Address : %06x\n", mm->addr);
} else if (mm->msgtype == 4 || mm->msgtype == 20) {
printf("DF %d: %s, Altitude Reply.\n", mm->msgtype,
(mm->msgtype == 4) ? "Surveillance" : "Comm-B");
printf(" Flight Status : %s\n", fs_str[mm->fs]);
printf(" DR : %d\n", ((mm->msg[1] >> 3) & 0x1F));
printf(" UM : %d\n", (((mm->msg[1] & 7) << 3) | (mm->msg[2] >> 5)));
printf(" Altitude : %d %s\n", mm->altitude,
(mm->unit == MODES_UNIT_METERS) ? "meters" : "feet");
printf(" ICAO Address : %06x\n", mm->addr);
if (mm->msgtype == 20) {
printf(" Comm-B BDS : %x\n", mm->msg[4]);
// Decode the extended squitter message
if ( mm->msg[4] == 0x20) { // BDS 2,0 Aircraft identification
printf(" BDS 2,0 Aircraft Identification : %s\n", mm->flight);
}
}
} else if (mm->msgtype == 5 || mm->msgtype == 21) {
printf("DF %d: %s, Identity Reply.\n", mm->msgtype,
(mm->msgtype == 5) ? "Surveillance" : "Comm-B");
printf(" Flight Status : %s\n", fs_str[mm->fs]);
printf(" DR : %d\n", ((mm->msg[1] >> 3) & 0x1F));
printf(" UM : %d\n", (((mm->msg[1] & 7) << 3) | (mm->msg[2] >> 5)));
printf(" Squawk : %x\n", mm->modeA);
printf(" ICAO Address : %06x\n", mm->addr);
if (mm->msgtype == 21) {
printf(" Comm-B BDS : %x\n", mm->msg[4]);
// Decode the extended squitter message
if ( mm->msg[4] == 0x20) { // BDS 2,0 Aircraft identification
printf(" BDS 2,0 Aircraft Identification : %s\n", mm->flight);
}
}
} else if (mm->msgtype == 11) { // DF 11
printf("DF 11: All Call Reply.\n");
printf(" Capability : %d (%s)\n", mm->ca, ca_str[mm->ca]);
printf(" ICAO Address: %06x\n", mm->addr);
if (mm->iid > 16)
{printf(" IID : SI-%02d\n", mm->iid-16);}
else
{printf(" IID : II-%02d\n", mm->iid);}
} else if (mm->msgtype == 16) { // DF 16
printf("DF 16: Long Air to Air ACAS\n");
} else if (mm->msgtype == 17) { // DF 17
printf("DF 17: ADS-B message.\n");
printf(" Capability : %d (%s)\n", mm->ca, ca_str[mm->ca]);
printf(" ICAO Address : %06x\n", mm->addr);
printf(" Extended Squitter Type: %d\n", mm->metype);
printf(" Extended Squitter Sub : %d\n", mm->mesub);
printf(" Extended Squitter Name: %s\n", getMEDescription(mm->metype, mm->mesub));
// Decode the extended squitter message
if (mm->metype >= 1 && mm->metype <= 4) { // Aircraft identification
printf(" Aircraft Type : %c%d\n", ('A' + 4 - mm->metype), mm->mesub);
printf(" Identification : %s\n", mm->flight);
//} else if (mm->metype >= 5 && mm->metype <= 8) { // Surface position
} else if (mm->metype >= 9 && mm->metype <= 18) { // Airborne position Baro
printf(" F flag : %s\n", (mm->msg[6] & 0x04) ? "odd" : "even");
printf(" T flag : %s\n", (mm->msg[6] & 0x08) ? "UTC" : "non-UTC");
printf(" Altitude : %d feet\n", mm->altitude);
if (mm->bFlags & MODES_ACFLAGS_LATLON_VALID) {
printf(" Latitude : %f\n", mm->fLat);
printf(" Longitude: %f\n", mm->fLon);
} else {
printf(" Latitude : %d (not decoded)\n", mm->raw_latitude);
printf(" Longitude: %d (not decoded)\n", mm->raw_longitude);
}
} else if (mm->metype == 19) { // Airborne Velocity
if (mm->mesub == 1 || mm->mesub == 2) {
printf(" EW status : %s\n", (mm->bFlags & MODES_ACFLAGS_EWSPEED_VALID) ? "Valid" : "Unavailable");
printf(" EW velocity : %d\n", mm->ew_velocity);
printf(" NS status : %s\n", (mm->bFlags & MODES_ACFLAGS_NSSPEED_VALID) ? "Valid" : "Unavailable");
printf(" NS velocity : %d\n", mm->ns_velocity);
printf(" Vertical status : %s\n", (mm->bFlags & MODES_ACFLAGS_VERTRATE_VALID) ? "Valid" : "Unavailable");
printf(" Vertical rate src : %d\n", ((mm->msg[8] >> 4) & 1));
printf(" Vertical rate : %d\n", mm->vert_rate);
} else if (mm->mesub == 3 || mm->mesub == 4) {
printf(" Heading status : %s\n", (mm->bFlags & MODES_ACFLAGS_HEADING_VALID) ? "Valid" : "Unavailable");
printf(" Heading : %d\n", mm->heading);
printf(" Airspeed status : %s\n", (mm->bFlags & MODES_ACFLAGS_SPEED_VALID) ? "Valid" : "Unavailable");
printf(" Airspeed : %d\n", mm->velocity);
printf(" Vertical status : %s\n", (mm->bFlags & MODES_ACFLAGS_VERTRATE_VALID) ? "Valid" : "Unavailable");
printf(" Vertical rate src : %d\n", ((mm->msg[8] >> 4) & 1));
printf(" Vertical rate : %d\n", mm->vert_rate);
} else {
printf(" Unrecognized ME subtype: %d subtype: %d\n", mm->metype, mm->mesub);
}
//} else if (mm->metype >= 20 && mm->metype <= 22) { // Airborne position GNSS
} else {
printf(" Unrecognized ME type: %d subtype: %d\n", mm->metype, mm->mesub);
}
} else if (mm->msgtype == 18) { // DF 18
printf("DF 18: Extended Squitter.\n");
} else if (mm->msgtype == 19) { // DF 19
printf("DF 19: Military Extended Squitter.\n");
} else if (mm->msgtype == 22) { // DF 22
printf("DF 22: Military Use.\n");
} else if (mm->msgtype == 24) { // DF 24
printf("DF 24: Comm D Extended Length Message.\n");
} else if (mm->msgtype == 32) { // DF 32 is special code we use for Mode A/C
printf("SSR : Mode A/C Reply.\n");
if (mm->fs & 0x0080) {
printf(" Mode A : %04x IDENT\n", mm->modeA);
} else {
printf(" Mode A : %04x\n", mm->modeA);
if (mm->bFlags & MODES_ACFLAGS_ALTITUDE_VALID)
{printf(" Mode C : %d feet\n", mm->altitude);}
}
} else {
printf("DF %d: Unknown DF Format.\n", mm->msgtype);
}
printf("\n");
}
/* Turn I/Q samples pointed by Modes.data into the magnitude vector
* pointed by Modes.magnitude. */
void computeMagnitudeVector(void) {
uint16_t *m = &Modes.magnitude[MODES_PREAMBLE_SAMPLES+MODES_LONG_MSG_SAMPLES];
uint16_t *p = Modes.data;
uint32_t j;
memcpy(Modes.magnitude,&Modes.magnitude[MODES_ASYNC_BUF_SAMPLES], MODES_PREAMBLE_SIZE+MODES_LONG_MSG_SIZE);
/* Compute the magnitudo vector. It's just SQRT(I^2 + Q^2), but
* we rescale to the 0-255 range to exploit the full resolution. */
for (j = 0; j < MODES_ASYNC_BUF_SAMPLES; j ++) {
*m++ = Modes.maglut[*p++];
}
}
/* Return -1 if the message is out of fase left-side
* Return 1 if the message is out of fase right-size
* Return 0 if the message is not particularly out of phase.
*
* Note: this function will access pPreamble[-1], so the caller should make sure to
* call it only if we are not at the start of the current buffer. */
int detectOutOfPhase(uint16_t *pPreamble) {
if (pPreamble[ 3] > pPreamble[2]/3) return 1;
if (pPreamble[10] > pPreamble[9]/3) return 1;
if (pPreamble[ 6] > pPreamble[7]/3) return -1;
if (pPreamble[-1] > pPreamble[1]/3) return -1;
return 0;
}
/* This function does not really correct the phase of the message, it just
* applies a transformation to the first sample representing a given bit:
*
* If the previous bit was one, we amplify it a bit.
* If the previous bit was zero, we decrease it a bit.
*
* This simple transformation makes the message a bit more likely to be
* correctly decoded for out of phase messages:
*
* When messages are out of phase there is more uncertainty in
* sequences of the same bit multiple times, since 11111 will be
* transmitted as continuously altering magnitude (high, low, high, low...)
*
* However because the message is out of phase some part of the high
* is mixed in the low part, so that it is hard to distinguish if it is
* a zero or a one.
*
* However when the message is out of phase passing from 0 to 1 or from
* 1 to 0 happens in a very recognizable way, for instance in the 0 -> 1
* transition, magnitude goes low, high, high, low, and one of of the
* two middle samples the high will be *very* high as part of the previous
* or next high signal will be mixed there.
*
* Applying our simple transformation we make more likely if the current
* bit is a zero, to detect another zero. Symmetrically if it is a one
* it will be more likely to detect a one because of the transformation.
* In this way similar levels will be interpreted more likely in the
* correct way. */
void applyPhaseCorrection(uint16_t *pPayload) {
int j;
for (j = 0; j < MODES_LONG_MSG_SAMPLES; j += 2, pPayload += 2) {
if (pPayload[0] > pPayload[1]) { /* One */
pPayload[2] = (pPayload[2] * 5) / 4;
} else { /* Zero */
pPayload[2] = (pPayload[2] * 4) / 5;
}
}
}
/* Detect a Mode S messages inside the magnitude buffer pointed by 'm' and of
* size 'mlen' bytes. Every detected Mode S message is convert it into a
* stream of bits and passed to the function to display it. */
void detectModeS(uint16_t *m, uint32_t mlen) {
unsigned char msg[MODES_LONG_MSG_BYTES], *pMsg;
uint16_t aux[MODES_LONG_MSG_SAMPLES];
uint32_t j;
int use_correction = 0;
/* The Mode S preamble is made of impulses of 0.5 microseconds at
* the following time offsets:
*
* 0 - 0.5 usec: first impulse.
* 1.0 - 1.5 usec: second impulse.
* 3.5 - 4 usec: third impulse.
* 4.5 - 5 usec: last impulse.
*
* Since we are sampling at 2 Mhz every sample in our magnitude vector
* is 0.5 usec, so the preamble will look like this, assuming there is
* an impulse at offset 0 in the array:
*
* 0 -----------------
* 1 -
* 2 ------------------
* 3 --
* 4 -
* 5 --
* 6 -
* 7 ------------------
* 8 --
* 9 -------------------
*/
for (j = 0; j < mlen; j++) {
int high, i, errors, errors56, errorsTy;
int good_message = 0;
uint16_t *pPreamble, *pPayload, *pPtr;
uint8_t theByte, theErrs;
int msglen, scanlen, sigStrength;
pPreamble = &m[j];
pPayload = &m[j+MODES_PREAMBLE_SAMPLES];
if (!use_correction) // This is not a re-try with phase correction
{ // so try to find a new preamble
if (Modes.mode_ac)
{
struct modesMessage mm;
int ModeA = detectModeA(pPreamble, &mm);
if (ModeA) // We have found a valid ModeA/C in the data
{
mm.timestampMsg = Modes.timestampBlk + ((j+1) * 6);
// Decode the received message
decodeModeAMessage(&mm, ModeA);
// Pass data to the next layer
useModesMessage(&mm);
j += MODEAC_MSG_SAMPLES;
Modes.stat_ModeAC++;
continue;
}
}
/* First check of relations between the first 10 samples
* representing a valid preamble. We don't even investigate further
* if this simple test is not passed. */
if (!(pPreamble[0] > pPreamble[1] &&
pPreamble[1] < pPreamble[2] &&
pPreamble[2] > pPreamble[3] &&
pPreamble[3] < pPreamble[0] &&
pPreamble[4] < pPreamble[0] &&
pPreamble[5] < pPreamble[0] &&
pPreamble[6] < pPreamble[0] &&
pPreamble[7] > pPreamble[8] &&
pPreamble[8] < pPreamble[9] &&
pPreamble[9] > pPreamble[6]))
{
if (Modes.debug & MODES_DEBUG_NOPREAMBLE &&
*pPreamble > MODES_DEBUG_NOPREAMBLE_LEVEL)
dumpRawMessage("Unexpected ratio among first 10 samples", msg, m, j);
continue;
}
/* The samples between the two spikes must be < than the average
* of the high spikes level. We don't test bits too near to
* the high levels as signals can be out of phase so part of the
* energy can be in the near samples. */
high = (pPreamble[0] + pPreamble[2] + pPreamble[7] + pPreamble[9]) / 6;
if (pPreamble[4] >= high ||
pPreamble[5] >= high)
{
if (Modes.debug & MODES_DEBUG_NOPREAMBLE &&
*pPreamble > MODES_DEBUG_NOPREAMBLE_LEVEL)
dumpRawMessage("Too high level in samples between 3 and 6", msg, m, j);
continue;
}
/* Similarly samples in the range 11-14 must be low, as it is the
* space between the preamble and real data. Again we don't test
* bits too near to high levels, see above. */
if (pPreamble[11] >= high ||
pPreamble[12] >= high ||
pPreamble[13] >= high ||
pPreamble[14] >= high)
{
if (Modes.debug & MODES_DEBUG_NOPREAMBLE &&
*pPreamble > MODES_DEBUG_NOPREAMBLE_LEVEL)
dumpRawMessage("Too high level in samples between 10 and 15", msg, m, j);
continue;
}
Modes.stat_valid_preamble++;
}
else {
/* If the previous attempt with this message failed, retry using
* magnitude correction. */
// Make a copy of the Payload, and phase correct the copy
memcpy(aux, pPayload, sizeof(aux));
applyPhaseCorrection(aux);
Modes.stat_out_of_phase++;
pPayload = aux;
/* TODO ... apply other kind of corrections. */
}
/* Decode all the next 112 bits, regardless of the actual message
* size. We'll check the actual message type later. */
pMsg = &msg[0];
pPtr = pPayload;
theByte = 0;
theErrs = 0; errorsTy = 0;
errors = 0; errors56 = 0;
// We should have 4 'bits' of 0/1 and 1/0 samples in the preamble,
// so include these in the signal strength
sigStrength = (pPreamble[0]-pPreamble[1])
+ (pPreamble[2]-pPreamble[3])
+ (pPreamble[7]-pPreamble[6])
+ (pPreamble[9]-pPreamble[8]);
msglen = scanlen = MODES_LONG_MSG_BITS;
for (i = 0; i < scanlen; i++) {
uint32_t a = *pPtr++;
uint32_t b = *pPtr++;
if (a > b)
{theByte |= 1; if (i < 56) {sigStrength += (a-b);}}
else if (a < b)
{/*theByte |= 0;*/ if (i < 56) {sigStrength += (b-a);}}
else if (i >= MODES_SHORT_MSG_BITS) //(a == b), and we're in the long part of a frame
{errors++; /*theByte |= 0;*/}
else if (i >= 5) //(a == b), and we're in the short part of a frame
{scanlen = MODES_LONG_MSG_BITS; errors56 = ++errors;/*theByte |= 0;*/}
else if (i) //(a == b), and we're in the message type part of a frame
{errorsTy = errors56 = ++errors; theErrs |= 1; /*theByte |= 0;*/}
else //(a == b), and we're in the first bit of the message type part of a frame
{errorsTy = errors56 = ++errors; theErrs |= 1; theByte |= 1;}
if ((i & 7) == 7)
{*pMsg++ = theByte;}
else if (i == 4) {
msglen = modesMessageLenByType(theByte);
if (errors == 0)
{scanlen = msglen;}
}
theByte = theByte << 1;
if (i < 7)
{theErrs = theErrs << 1;}
// If we've exceeded the permissible number of encoding errors, abandon ship now
if (errors > MODES_MSG_ENCODER_ERRS) {
if (i < MODES_SHORT_MSG_BITS) {
msglen = 0;
} else if ((errorsTy == 1) && (theErrs == 0x80)) {
// If we only saw one error in the first bit of the byte of the frame, then it's possible
// we guessed wrongly about the value of the bit. We may be able to correct it by guessing
// the other way.
//
// We guessed a '1' at bit 7, which is the DF length bit == 112 Bits.
// Inverting bit 7 will change the message type from a long to a short.
// Invert the bit, cross your fingers and carry on.
msglen = MODES_SHORT_MSG_BITS;
msg[0] ^= theErrs; errorsTy = 0;
errors = errors56; // revert to the number of errors prior to bit 56
Modes.stat_DF_Len_Corrected++;
} else if (i < MODES_LONG_MSG_BITS) {
msglen = MODES_SHORT_MSG_BITS;
errors = errors56;
} else {
msglen = MODES_LONG_MSG_BITS;
}
break;
}
}
// Ensure msglen is consistent with the DF type
i = modesMessageLenByType(msg[0] >> 3);
if (msglen > i) {msglen = i;}
else if (msglen < i) {msglen = 0;}
//
// If we guessed at any of the bits in the DF type field, then look to see if our guess was sensible.
// Do this by looking to see if the original guess results in the DF type being one of the ICAO defined
// message types. If it isn't then toggle the guessed bit and see if this new value is ICAO defined.
// if the new value is ICAO defined, then update it in our message.
if ((msglen) && (errorsTy == 1) && (theErrs & 0x78)) {
// We guessed at one (and only one) of the message type bits. See if our guess is "likely"
// to be correct by comparing the DF against a list of known good DF's
int thisDF = ((theByte = msg[0]) >> 3) & 0x1f;
uint32_t validDFbits = 0x017F0831; // One bit per 32 possible DF's. Set bits 0,4,5,11,16.17.18.19,20,21,22,24
uint32_t thisDFbit = (1 << thisDF);
if (0 == (validDFbits & thisDFbit)) {
// The current DF is not ICAO defined, so is probably an errors.
// Toggle the bit we guessed at and see if the resultant DF is more likely
theByte ^= theErrs;
thisDF = (theByte >> 3) & 0x1f;
thisDFbit = (1 << thisDF);
// if this DF any more likely?
if (validDFbits & thisDFbit) {
// Yep, more likely, so update the main message
msg[0] = theByte;
Modes.stat_DF_Type_Corrected++;
errors--; // decrease the error count so we attempt to use the modified DF.
}
}
}
// We measured signal strength over the first 56 bits. Don't forget to add 4
// for the preamble samples, so round up and divide by 60.
sigStrength = (sigStrength + 29) / 60;
// When we reach this point, if error is small, and the signal strength is large enough
// we may have a Mode S message on our hands. It may still be broken and the CRC may not
// be correct, but this can be handled by the next layer.
if ( (msglen)
&& (sigStrength > MODES_MSG_SQUELCH_LEVEL)
&& (errors <= MODES_MSG_ENCODER_ERRS) ) {
struct modesMessage mm;
memset(&mm, 0, sizeof(mm));
// Set initial mm structure details
mm.timestampMsg = Modes.timestampBlk + (j*6);
sigStrength = (sigStrength + 0x7F) >> 8;
mm.signalLevel = ((sigStrength < 255) ? sigStrength : 255);
// Decode the received message
decodeModesMessage(&mm, msg);
// Update statistics
if (Modes.stats) {
if (mm.crcok || use_correction) {
if (errors == 0) Modes.stat_demodulated++;
if (mm.correctedbits == 0) {
if (mm.crcok) {Modes.stat_goodcrc++;}
else {Modes.stat_badcrc++;}
} else {
Modes.stat_badcrc++;
Modes.stat_fixed++;
if (mm.correctedbits == 1) {
Modes.stat_single_bit_fix++;
} else if (mm.correctedbits == 2) {
Modes.stat_two_bits_fix++;
}
}
}
}
// Output debug mode info if needed
if (use_correction) {
if (Modes.debug & MODES_DEBUG_DEMOD)
dumpRawMessage("Demodulated with 0 errors", msg, m, j);
else if (Modes.debug & MODES_DEBUG_BADCRC &&
mm.msgtype == 17 &&
(!mm.crcok || mm.correctedbits != 0))
dumpRawMessage("Decoded with bad CRC", msg, m, j);
else if (Modes.debug & MODES_DEBUG_GOODCRC && mm.crcok &&
mm.correctedbits == 0)
dumpRawMessage("Decoded with good CRC", msg, m, j);
}
// Skip this message if we are sure it's fine
if (mm.crcok) {
j += (MODES_PREAMBLE_US+msglen)*2;
good_message = 1;
if (use_correction)
mm.phase_corrected = 1;
}
// Pass data to the next layer
useModesMessage(&mm);
} else {
if (Modes.debug & MODES_DEBUG_DEMODERR && use_correction) {
printf("The following message has %d demod errors\n", errors);
dumpRawMessage("Demodulated with errors", msg, m, j);
}
}
// Retry with phase correction if possible.
if (!good_message && !use_correction && j && detectOutOfPhase(pPreamble)) {
use_correction = 1; j--;
} else {
use_correction = 0;
}
}
//Send any remaining partial raw buffers now
if (Modes.rawOutUsed)
{
Modes.net_output_raw_rate_count++;
if (Modes.net_output_raw_rate_count > Modes.net_output_raw_rate)
{
modesSendAllClients(Modes.ros, Modes.rawOut, Modes.rawOutUsed);
Modes.rawOutUsed = 0;
Modes.net_output_raw_rate_count = 0;
}
}
}
//
// When a new message is available, because it was decoded from the RTL device,
// file, or received in the TCP input port, or any other way we can receive a
// decoded message, we call this function in order to use the message.
//
// Basically this function passes a raw message to the upper layers for further
// processing and visualization
//
void useModesMessage(struct modesMessage *mm) {
if ((Modes.check_crc == 0) || (mm->crcok)) {
// Track aircrafts if...
if ( (Modes.interactive) // in interactive mode
|| (Modes.stat_http_requests) // or if the HTTP interface is enabled
|| (Modes.stat_sbs_connections) // or if sbs connections are established
|| (Modes.mode_ac) ) { // or if mode A/C decoding is enabled
interactiveReceiveData(mm);
}
// In non-interactive non-quiet mode, display messages on standard output
if (!Modes.interactive && !Modes.quiet) {
displayModesMessage(mm);
}
// Feed SBS output clients
if (Modes.stat_sbs_connections) {
modesSendSBSOutput(mm);
}
// Send data to connected network clients
if (Modes.net) {
if (Modes.beast) {
modesSendBeastOutput(mm);
} else {
modesSendRawOutput(mm);
}
}
}
}
/* ========================= Interactive mode =============================== */
//
// Return a new aircraft structure for the interactive mode linked list
// of aircraft
//
struct aircraft *interactiveCreateAircraft(struct modesMessage *mm) {
struct aircraft *a = (struct aircraft *) malloc(sizeof(*a));
// Default everything to zero/NULL
memset(a, 0, sizeof(*a));
// Now initialise things that should not be 0/NULL to their defaults
a->addr = mm->addr;
a->lat = a->lon = 0.0;
memset(a->signalLevel, mm->signalLevel, 8); // First time, initialise everything
// to the first signal strength
// mm->msgtype 32 is used to represent Mode A/C. These values can never change, so
// set them once here during initialisation, and don't bother to set them every
// time this ModeA/C is received again in the future
if (mm->msgtype == 32) {
int modeC = ModeAToModeC(mm->modeA | mm->fs);
a->modeACflags = MODEAC_MSG_FLAG;
if (modeC < -12) {
a->modeACflags |= MODEAC_MSG_MODEA_ONLY;
} else {
mm->altitude = modeC * 100;
mm->bFlags |= MODES_ACFLAGS_ALTITUDE_VALID;
}
}
return (a);
}
//
// Return the aircraft with the specified address, or NULL if no aircraft
// exists with this address.
//
struct aircraft *interactiveFindAircraft(uint32_t addr) {
struct aircraft *a = Modes.aircrafts;
while(a) {
if (a->addr == addr) return (a);
a = a->next;
}
return (NULL);
}
//
// We have received a Mode A or C response.
//
// Search through the list of known Mode-S aircraft and tag them if this Mode A/C
// matches their known Mode S Squawks or Altitudes(+/- 50feet).
//
// A Mode S equipped aircraft may also respond to Mode A and Mode C SSR interrogations.
// We can't tell if this is a Mode A or C, so scan through the entire aircraft list
// looking for matches on Mode A (squawk) and Mode C (altitude). Flag in the Mode S
// records that we have had a potential Mode A or Mode C response from this aircraft.
//
// If an aircraft responds to Mode A then it's highly likely to be responding to mode C
// too, and vice verca. Therefore, once the mode S record is tagged with both a Mode A
// and a Mode C flag, we can be fairly confident that this Mode A/C frame relates to that
// Mode S aircraft.
//
// Mode C's are more likely to clash than Mode A's; There could be several aircraft
// cruising at FL370, but it's less likely (though not impossible) that there are two
// aircraft on the same squawk. Therefore, give precidence to Mode A record matches
//
// Note : It's theoretically possible for an aircraft to have the same value for Mode A
// and Mode C. Therefore we have to check BOTH A AND C for EVERY S.
//
void interactiveUpdateAircraftModeA(struct aircraft *a) {
struct aircraft *b = Modes.aircrafts;
while(b) {
if ((b->modeACflags & MODEAC_MSG_FLAG) == 0) {// skip any fudged ICAO records
// If both (a) and (b) have valid squawks...
if ((a->bFlags & b->bFlags) & MODES_ACFLAGS_SQUAWK_VALID) {
// ...check for Mode-A == Mode-S Squawk matches
if (a->modeA == b->modeA) { // If a 'real' Mode-S ICAO exists using this Mode-A Squawk
b->modeAcount = a->messages;
b->modeACflags |= MODEAC_MSG_MODEA_HIT;
a->modeACflags |= MODEAC_MSG_MODEA_HIT;
if ( (b->modeAcount > 0) &&
( (b->modeCcount > 1)
|| (a->modeACflags & MODEAC_MSG_MODEA_ONLY)) ) // Allow Mode-A only matches if this Mode-A is invalid Mode-C
{a->modeACflags |= MODEAC_MSG_MODES_HIT;} // flag this ModeA/C probably belongs to a known Mode S
}
}
// If both (a) and (b) have valid altitudes...
if ((a->bFlags & b->bFlags) & MODES_ACFLAGS_ALTITUDE_VALID) {
// ... check for Mode-C == Mode-S Altitude matches
if ( (a->modeC == b->modeC ) // If a 'real' Mode-S ICAO exists at this Mode-C Altitude
|| (a->modeC == b->modeC + 1) // or this Mode-C - 100 ft
|| (a->modeC + 1 == b->modeC ) ) { // or this Mode-C + 100 ft
b->modeCcount = a->messages;
b->modeACflags |= MODEAC_MSG_MODEC_HIT;
a->modeACflags |= MODEAC_MSG_MODEC_HIT;
if ( (b->modeAcount > 0) &&
(b->modeCcount > 1) )
{a->modeACflags |= (MODEAC_MSG_MODES_HIT | MODEAC_MSG_MODEC_OLD);} // flag this ModeA/C probably belongs to a known Mode S
}
}
}
b = b->next;
}
}
void interactiveUpdateAircraftModeS() {
struct aircraft *a = Modes.aircrafts;
while(a) {
int flags = a->modeACflags;
if (flags & MODEAC_MSG_FLAG) { // find any fudged ICAO records
// clear the current A,C and S hit bits ready for this attempt
a->modeACflags = flags & ~(MODEAC_MSG_MODEA_HIT | MODEAC_MSG_MODEC_HIT | MODEAC_MSG_MODES_HIT);
interactiveUpdateAircraftModeA(a); // and attempt to match them with Mode-S
}
a = a->next;
}
}
/* Always positive MOD operation, used for CPR decoding. */
int cprModFunction(int a, int b) {
int res = a % b;
if (res < 0) res += b;
return res;
}
/* The NL function uses the precomputed table from 1090-WP-9-14 */
int cprNLFunction(double lat) {
if (lat < 0) lat = -lat; /* Table is simmetric about the equator. */
if (lat < 10.47047130) return 59;
if (lat < 14.82817437) return 58;
if (lat < 18.18626357) return 57;
if (lat < 21.02939493) return 56;
if (lat < 23.54504487) return 55;
if (lat < 25.82924707) return 54;
if (lat < 27.93898710) return 53;
if (lat < 29.91135686) return 52;
if (lat < 31.77209708) return 51;
if (lat < 33.53993436) return 50;
if (lat < 35.22899598) return 49;
if (lat < 36.85025108) return 48;
if (lat < 38.41241892) return 47;
if (lat < 39.92256684) return 46;
if (lat < 41.38651832) return 45;
if (lat < 42.80914012) return 44;
if (lat < 44.19454951) return 43;
if (lat < 45.54626723) return 42;
if (lat < 46.86733252) return 41;
if (lat < 48.16039128) return 40;
if (lat < 49.42776439) return 39;
if (lat < 50.67150166) return 38;
if (lat < 51.89342469) return 37;
if (lat < 53.09516153) return 36;
if (lat < 54.27817472) return 35;
if (lat < 55.44378444) return 34;
if (lat < 56.59318756) return 33;
if (lat < 57.72747354) return 32;
if (lat < 58.84763776) return 31;
if (lat < 59.95459277) return 30;
if (lat < 61.04917774) return 29;
if (lat < 62.13216659) return 28;
if (lat < 63.20427479) return 27;
if (lat < 64.26616523) return 26;
if (lat < 65.31845310) return 25;
if (lat < 66.36171008) return 24;
if (lat < 67.39646774) return 23;
if (lat < 68.42322022) return 22;
if (lat < 69.44242631) return 21;
if (lat < 70.45451075) return 20;
if (lat < 71.45986473) return 19;
if (lat < 72.45884545) return 18;
if (lat < 73.45177442) return 17;
if (lat < 74.43893416) return 16;
if (lat < 75.42056257) return 15;
if (lat < 76.39684391) return 14;
if (lat < 77.36789461) return 13;
if (lat < 78.33374083) return 12;
if (lat < 79.29428225) return 11;
if (lat < 80.24923213) return 10;
if (lat < 81.19801349) return 9;
if (lat < 82.13956981) return 8;
if (lat < 83.07199445) return 7;
if (lat < 83.99173563) return 6;
if (lat < 84.89166191) return 5;
if (lat < 85.75541621) return 4;
if (lat < 86.53536998) return 3;
if (lat < 87.00000000) return 2;
else return 1;
}
int cprNFunction(double lat, int fflag) {
int nl = cprNLFunction(lat) - (fflag ? 1 : 0);
if (nl < 1) nl = 1;
return nl;
}
double cprDlonFunction(double lat, int fflag, int surface) {
return (surface ? 90.0 : 360.0) / cprNFunction(lat, fflag);
}
/* This algorithm comes from:
* http://www.lll.lu/~edward/edward/adsb/DecodingADSBposition.html.
*
* A few remarks:
* 1) 131072 is 2^17 since CPR latitude and longitude are encoded in 17 bits.
* 2) We assume that we always received the odd packet as last packet for
* simplicity. This may provide a position that is less fresh of a few
* seconds.
*/
void decodeCPR(struct aircraft *a, int fflag, int surface) {
double AirDlat0 = (surface ? 90.0 : 360.0) / 60.0;
double AirDlat1 = (surface ? 90.0 : 360.0) / 59.0;
double lat0 = a->even_cprlat;
double lat1 = a->odd_cprlat;
double lon0 = a->even_cprlon;
double lon1 = a->odd_cprlon;
// Compute the Latitude Index "j"
int j = (int) floor(((59*lat0 - 60*lat1) / 131072) + 0.5);
double rlat0 = AirDlat0 * (cprModFunction(j,60) + lat0 / 131072);
double rlat1 = AirDlat1 * (cprModFunction(j,59) + lat1 / 131072);
if (surface) {
// If we're on the ground, make sure we have our receiver base station Lat/Lon
if (0 == (Modes.bUserFlags & MODES_USER_LATLON_VALID))
{return;}
rlat0 += floor(Modes.fUserLat / 90.0) * 90.0; // Move from 1st quadrant to our quadrant
rlat1 += floor(Modes.fUserLat / 90.0) * 90.0;
} else {
if (rlat0 >= 270) rlat0 -= 360;
if (rlat1 >= 270) rlat1 -= 360;
}
// Check that both are in the same latitude zone, or abort.
if (cprNLFunction(rlat0) != cprNLFunction(rlat1)) return;
// Compute ni and the Longitude Index "m"
if (fflag) { // Use odd packet.
int ni = cprNFunction(rlat1,1);
int m = (int) floor((((lon0 * (cprNLFunction(rlat1)-1)) -
(lon1 * cprNLFunction(rlat1))) / 131072.0) + 0.5);
a->lon = cprDlonFunction(rlat1, 1, surface) * (cprModFunction(m, ni)+lon1/131072);
a->lat = rlat1;
} else { // Use even packet.
int ni = cprNFunction(rlat0,0);
int m = (int) floor((((lon0 * (cprNLFunction(rlat0)-1)) -
(lon1 * cprNLFunction(rlat0))) / 131072) + 0.5);
a->lon = cprDlonFunction(rlat0, 0, surface) * (cprModFunction(m, ni)+lon0/131072);
a->lat = rlat0;
}
if (surface) {
a->lon += floor(Modes.fUserLon / 90.0) * 90.0; // Move from 1st quadrant to our quadrant
} else if (a->lon > 180) {
a->lon -= 360;
}
a->seenLatLon = a->seen;
a->timestampLatLon = a->timestamp;
a->bFlags |= (MODES_ACFLAGS_LATLON_VALID | MODES_ACFLAGS_LATLON_REL_OK);
}
/* This algorithm comes from:
* 1090-WP29-07-Draft_CPR101 (which also defines decodeCPR() )
*
* There is an error in this document related to CPR relative decode.
* Should use trunc() rather than the floor() function in Eq 38 and related for deltaZI.
* floor() returns integer less than argument
* trunc() returns integer closer to zero than argument.
* Note: text of document describes trunc() functionality for deltaZI calculation
* but the formulae use floor().
*/
int decodeCPRrelative(struct aircraft *a, int fflag, int surface) {
double AirDlat;
double AirDlon;
double lat;
double lon;
double lonr, latr;
double rlon, rlat;
int j,m;
if (a->bFlags & MODES_ACFLAGS_LATLON_REL_OK) { // Ok to try aircraft relative first
latr = a->lat;
lonr = a->lon;
} else if (Modes.bUserFlags & MODES_USER_LATLON_VALID) { // Try ground station relative next
latr = Modes.fUserLat;
lonr = Modes.fUserLon;
} else {
return (-1); // Exit with error - can't do relative if we don't have ref.
}
if (fflag) { // odd
AirDlat = (surface ? 90.0 : 360.0) / 59.0;
lat = a->odd_cprlat;
lon = a->odd_cprlon;
} else { // even
AirDlat = (surface ? 90.0 : 360.0) / 60.0;
lat = a->even_cprlat;
lon = a->even_cprlon;
}
// Compute the Latitude Index "j"
j = (int) (floor(latr/AirDlat) +
trunc(0.5 + cprModFunction((int)latr, (int)AirDlat)/AirDlat - lat/131072));
rlat = AirDlat * (j + lat/131072);
if (rlat >= 270) rlat -= 360;
// Check to see that answer is reasonable - ie no more than 1/2 cell away
if (fabs(rlat - a->lat) > (AirDlat/2)) {
a->bFlags &= ~MODES_ACFLAGS_LATLON_REL_OK; // This will cause a quick exit next time if no global has been done
return (-1); // Time to give up - Latitude error
}
// Compute the Longitude Index "m"
AirDlon = cprDlonFunction(rlat, fflag, surface);
m = (int) (floor(lonr/AirDlon) +
trunc(0.5 + cprModFunction((int)lonr, (int)AirDlon)/AirDlon - lon/131072));
rlon = AirDlon * (m + lon/131072);
if (rlon > 180) rlon -= 360;
// Check to see that answer is reasonable - ie no more than 1/2 cell away
if (fabs(rlon - a->lon) > (AirDlon/2)) {
a->bFlags &= ~MODES_ACFLAGS_LATLON_REL_OK; // This will cause a quick exit next time if no global has been done
return (-1); // Time to give up - Longitude error
}
a->lat = rlat;
a->lon = rlon;
a->seenLatLon = a->seen;
a->timestampLatLon = a->timestamp;
a->bFlags |= (MODES_ACFLAGS_LATLON_VALID | MODES_ACFLAGS_LATLON_REL_OK);
return (0);
}
/* Receive new messages and populate the interactive mode with more info. */
struct aircraft *interactiveReceiveData(struct modesMessage *mm) {
struct aircraft *a, *aux;
if (Modes.check_crc && mm->crcok == 0) return NULL;
// Loookup our aircraft or create a new one
a = interactiveFindAircraft(mm->addr);
if (!a) { // If it's a currently unknown aircraft....
a = interactiveCreateAircraft(mm); // ., create a new record for it,
a->next = Modes.aircrafts; // .. and put it at the head of the list
Modes.aircrafts = a;
} else {
/* If it is an already known aircraft, move it on head
* so we keep aircrafts ordered by received message time.
*
* However move it on head only if at least one second elapsed
* since the aircraft that is currently on head sent a message,
* othewise with multiple aircrafts at the same time we have an
* useless shuffle of positions on the screen. */
if (0 && Modes.aircrafts != a && (time(NULL) - a->seen) >= 1) {
aux = Modes.aircrafts;
while(aux->next != a) aux = aux->next;
/* Now we are a node before the aircraft to remove. */
aux->next = aux->next->next; /* removed. */
/* Add on head */
a->next = Modes.aircrafts;
Modes.aircrafts = a;
}
}
a->signalLevel[a->messages & 7] = mm->signalLevel;// replace the 8th oldest signal strength
a->seen = time(NULL);
a->timestamp = mm->timestampMsg;
a->messages++;
// If a (new) CALLSIGN has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_CALLSIGN_VALID) {
memcpy(a->flight, mm->flight, sizeof(a->flight));
}
// If a (new) ALTITUDE has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_ALTITUDE_VALID) {
if ( (a->modeCcount) // if we've a modeCcount already
&& (a->altitude != mm->altitude ) ) // and Altitude has changed
// && (a->modeC != mm->modeC + 1) // and Altitude not changed by +100 feet
// && (a->modeC + 1 != mm->modeC ) ) // and Altitude not changes by -100 feet
{
a->modeCcount = 0; //....zero the hit count
a->modeACflags &= ~MODEAC_MSG_MODEC_HIT;
}
a->altitude = mm->altitude;
a->modeC = (mm->altitude + 49) / 100;
}
// If a (new) SQUAWK has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_SQUAWK_VALID) {
if (a->modeA != mm->modeA) {
a->modeAcount = 0; // Squawk has changed, so zero the hit count
a->modeACflags &= ~MODEAC_MSG_MODEA_HIT;
}
a->modeA = mm->modeA;
}
// If a (new) HEADING has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_HEADING_VALID) {
a->track = mm->heading;
}
// If a (new) SPEED has been received, copy it to the aircraft structure
if (mm->bFlags & MODES_ACFLAGS_SPEED_VALID) {
a->speed = mm->velocity;
}
// if the Aircraft has landed or taken off since the last message, clear the even/odd CPR flags
if ((mm->bFlags & MODES_ACFLAGS_AOG_VALID) && ((a->bFlags ^ mm->bFlags) & MODES_ACFLAGS_AOG)) {
a->bFlags &= ~(MODES_ACFLAGS_LLBOTH_VALID | MODES_ACFLAGS_AOG);
} else if ( (mm->bFlags & MODES_ACFLAGS_LLEITHER_VALID)
&& (((mm->bFlags | a->bFlags) & MODES_ACFLAGS_LLEITHER_VALID) == MODES_ACFLAGS_LLBOTH_VALID) ) {
// If it's a new even/odd raw lat/lon, and we now have both even and odd,decode the CPR
int fflag;
if (mm->bFlags & MODES_ACFLAGS_LLODD_VALID) {
fflag = 1;
a->odd_cprlat = mm->raw_latitude;
a->odd_cprlon = mm->raw_longitude;
a->odd_cprtime = mstime();
} else {
fflag = 0;
a->even_cprlat = mm->raw_latitude;
a->even_cprlon = mm->raw_longitude;
a->even_cprtime = mstime();
}
// Try relative CPR first
if (decodeCPRrelative(a, fflag, (mm->bFlags & MODES_ACFLAGS_AOG))) {
// If it fails then try global if the two data are less than 10 seconds apart
if (abs((int)(a->even_cprtime - a->odd_cprtime)) <= 10000) {
decodeCPR(a, fflag, (mm->bFlags & MODES_ACFLAGS_AOG));
}
}
//If we sucessfully decoded, back copy the results to mm so that we can print them in list output
if (a->bFlags & MODES_ACFLAGS_LATLON_VALID) {
mm->bFlags |= MODES_ACFLAGS_LATLON_VALID;
mm->fLat = a->lat;
mm->fLon = a->lon;
}
}
// Update the aircrafts a->bFlags to reflect the newly received mm->bFlags;
a->bFlags |= mm->bFlags;
if (mm->msgtype == 32) {
int flags = a->modeACflags;
if ((flags & (MODEAC_MSG_MODEC_HIT | MODEAC_MSG_MODEC_OLD)) == MODEAC_MSG_MODEC_OLD) {
//
// This Mode-C doesn't currently hit any known Mode-S, but it used to because MODEAC_MSG_MODEC_OLD is
// set So the aircraft it used to match has either changed altitude, or gone out of our receiver range
//
// We've now received this Mode-A/C again, so it must be a new aircraft. It could be another aircraft
// at the same Mode-C altitude, or it could be a new airctraft with a new Mods-A squawk.
//
// To avoid masking this aircraft from the interactive display, clear the MODEAC_MSG_MODES_OLD flag
// and set messages to 1;
//
a->modeACflags = flags & ~MODEAC_MSG_MODEC_OLD;
a->messages = 1;
}
}
return (a);
}
/* Show the currently captured interactive data on screen. */
void interactiveShowData(void) {
struct aircraft *a = Modes.aircrafts;
time_t now = time(NULL);
int count = 0;
char progress;
char spinner[4] = "|/-\\";
progress = spinner[time(NULL)%4];
printf("\x1b[H\x1b[2J"); /* Clear the screen */
if (Modes.interactive_rtl1090 == 0) {
printf (
"Hex Mode Sqwk Flight Alt Spd Hdg Lat Long Sig Msgs Ti%c\n", progress);
} else {
printf (
"Hex Flight Alt V/S GS TT SSR G*456^ Msgs Seen %c\n", progress);
}
printf(
"-------------------------------------------------------------------------------\n");
while(a && count < Modes.interactive_rows) {
int msgs = a->messages;
int flags = a->modeACflags;
if ( (((flags & (MODEAC_MSG_FLAG )) == 0 ) )
|| (((flags & (MODEAC_MSG_MODES_HIT | MODEAC_MSG_MODEA_ONLY)) == MODEAC_MSG_MODEA_ONLY) && (msgs > 4 ) )
|| (((flags & (MODEAC_MSG_MODES_HIT | MODEAC_MSG_MODEC_OLD )) == 0 ) && (msgs > 127) )
) {
int altitude = a->altitude, speed = a->speed;
char strSquawk[5] = " ";
char strFl[6] = " ";
char strTt[5] = " ";
char strGs[5] = " ";
// Convert units to metric if --metric was specified
if (Modes.metric) {
altitude = (int) (altitude / 3.2828);
speed = (int) (speed * 1.852);
}
if (a->bFlags & MODES_ACFLAGS_SQUAWK_VALID) {
snprintf(strSquawk,5,"%04x", a->modeA);}
if (a->bFlags & MODES_ACFLAGS_SPEED_VALID) {
snprintf (strGs, 5,"%3d", speed);}
if (a->bFlags & MODES_ACFLAGS_HEADING_VALID) {
snprintf (strTt, 5,"%03d", a->track);}
if (msgs > 99999) {
msgs = 99999;}
if (Modes.interactive_rtl1090) { // RTL1090 display mode
if (a->bFlags & MODES_ACFLAGS_ALTITUDE_VALID) {
snprintf(strFl,6,"F%03d",(altitude/100));
}
printf("%06x %-8s %-4s %-3s %-3s %4s %-6d %-2d\n",
a->addr, a->flight, strFl, strGs, strTt, strSquawk, msgs, (int)(now - a->seen));
} else { // Dump1090 display mode
char strMode[5] = " ";
char strLat[8] = " ";
char strLon[9] = " ";
unsigned char * pSig = a->signalLevel;
unsigned int signalAverage = (pSig[0] + pSig[1] + pSig[2] + pSig[3] +
pSig[4] + pSig[5] + pSig[6] + pSig[7] + 3) >> 3;
if ((flags & MODEAC_MSG_FLAG) == 0) {
strMode[0] = 'S';
} else if (flags & MODEAC_MSG_MODEA_ONLY) {
strMode[0] = 'A';
}
if (flags & MODEAC_MSG_MODEA_HIT) {strMode[2] = 'a';}
if (flags & MODEAC_MSG_MODEC_HIT) {strMode[3] = 'c';}
if (a->bFlags & MODES_ACFLAGS_LATLON_VALID) {
snprintf(strLat, 8,"%7.03f", a->lat);
snprintf(strLon, 9,"%8.03f", a->lon);
}
if (a->bFlags & MODES_ACFLAGS_AOG) {
snprintf(strFl, 6," grnd");
} else if (a->bFlags & MODES_ACFLAGS_ALTITUDE_VALID) {
snprintf(strFl, 6, "%5d", altitude);
}
// printf("%06x %-4s %-4s %-8s %5d %3d %3d %7.03f %8.03f %3d %5d %2d\n",
// a->addr, strMode, strSquawk, a->flight, altitude, speed, a->track,
// a->lat, a->lon, signalAverage, msgs, (int)(now - a->seen));
printf("%06x %-4s %-4s %-8s %5s %3s %3s %7s %8s %3d %5d %2d\n",
a->addr, strMode, strSquawk, a->flight, strFl, strGs, strTt,
strLat, strLon, signalAverage, msgs, (int)(now - a->seen));
}
count++;
}
a = a->next;
}
}
/* When in interactive mode If we don't receive new nessages within
* MODES_INTERACTIVE_TTL seconds we remove the aircraft from the list. */
void interactiveRemoveStaleAircrafts(void) {
struct aircraft *a = Modes.aircrafts;
struct aircraft *prev = NULL;
time_t now = time(NULL);
while(a) {
if ((now - a->seen) > Modes.interactive_ttl) {
struct aircraft *next = a->next;
/* Remove the element from the linked list, with care
* if we are removing the first element. */
free(a);
if (!prev)
Modes.aircrafts = next;
else
prev->next = next;
a = next;
} else {
prev = a;
a = a->next;
}
}
}
/* ============================== Snip mode ================================= */
/* Get raw IQ samples and filter everything is < than the specified level
* for more than 256 samples in order to reduce example file size. */
void snipMode(int level) {
int i, q;
uint64_t c = 0;
while ((i = getchar()) != EOF && (q = getchar()) != EOF) {
if (abs(i-127) < level && abs(q-127) < level) {
c++;
if (c > MODES_PREAMBLE_SIZE) continue;
} else {
c = 0;
}
putchar(i);
putchar(q);
}
}
/* ============================= Networking =================================
* Note: here we risregard any kind of good coding practice in favor of
* extreme simplicity, that is:
*
* 1) We only rely on the kernel buffers for our I/O without any kind of
* user space buffering.
* 2) We don't register any kind of event handler, from time to time a
* function gets called and we accept new connections. All the rest is
* handled via non-blocking I/O and manually pullign clients to see if
* they have something new to share with us when reading is needed.
*/
/* Networking "stack" initialization. */
void modesInitNet(void) {
struct {
char *descr;
int *socket;
int port;
} services[4] = {
{"Raw TCP output", &Modes.ros, Modes.net_output_raw_port},
{"Raw TCP input", &Modes.ris, Modes.net_input_raw_port},
{"HTTP server", &Modes.https, Modes.net_http_port},
{"Basestation TCP output", &Modes.sbsos, Modes.net_output_sbs_port}
};
int j;
memset(Modes.clients,0,sizeof(Modes.clients));
Modes.maxfd = -1;
for (j = 0; j < 4; j++) {
int s = anetTcpServer(Modes.aneterr, services[j].port, NULL);
if (s == -1) {
fprintf(stderr, "Error opening the listening port %d (%s): %s\n",
services[j].port, services[j].descr, strerror(errno));
exit(1);
}
anetNonBlock(Modes.aneterr, s);
*services[j].socket = s;
}
signal(SIGPIPE, SIG_IGN);
}
/* This function gets called from time to time when the decoding thread is
* awakened by new data arriving. This usually happens a few times every
* second. */
void modesAcceptClients(void) {
int fd, port;
unsigned int j;
struct client *c;
int services[4];
services[0] = Modes.ros;
services[1] = Modes.ris;
services[2] = Modes.https;
services[3] = Modes.sbsos;
for (j = 0; j < sizeof(services)/sizeof(int); j++) {
fd = anetTcpAccept(Modes.aneterr, services[j], NULL, &port);
if (fd == -1) continue;
if (fd >= MODES_NET_MAX_FD) {
close(fd);
return; /* Max number of clients reached. */
}
anetNonBlock(Modes.aneterr, fd);
c = (struct client *) malloc(sizeof(*c));
c->service = services[j];
c->fd = fd;
c->buflen = 0;
Modes.clients[fd] = c;
anetSetSendBuffer(Modes.aneterr,fd,MODES_NET_SNDBUF_SIZE);
if (Modes.maxfd < fd) Modes.maxfd = fd;
if (services[j] == Modes.sbsos) Modes.stat_sbs_connections++;
j--; /* Try again with the same listening port. */
if (Modes.debug & MODES_DEBUG_NET)
printf("Created new client %d\n", fd);
}
}
/* On error free the client, collect the structure, adjust maxfd if needed. */
void modesFreeClient(int fd) {
close(fd);
free(Modes.clients[fd]);
Modes.clients[fd] = NULL;
if (Modes.debug & MODES_DEBUG_NET)
printf("Closing client %d\n", fd);
/* If this was our maxfd, rescan the full clients array to check what's
* the new max. */
if (Modes.maxfd == fd) {
int j;
Modes.maxfd = -1;
for (j = 0; j < MODES_NET_MAX_FD; j++) {
if (Modes.clients[j]) Modes.maxfd = j;
}
}
}
/* Send the specified message to all clients listening for a given service. */
void modesSendAllClients(int service, void *msg, int len) {
int j;
struct client *c;
for (j = 0; j <= Modes.maxfd; j++) {
c = Modes.clients[j];
if (c && c->service == service) {
int nwritten = write(j, msg, len);
if (nwritten != len) {
modesFreeClient(j);
}
}
}
}
/* Write raw output in Beast Binary format with Timestamp to TCP clients */
void modesSendBeastOutput(struct modesMessage *mm) {
char *p = &Modes.rawOut[Modes.rawOutUsed];
int msgLen = mm->msgbits / 8;
char * pTimeStamp;
int j;
*p++ = 0x1a;
if (msgLen == MODES_SHORT_MSG_BYTES)
{*p++ = '2';}
else if (msgLen == MODES_LONG_MSG_BYTES)
{*p++ = '3';}
else if (msgLen == MODEAC_MSG_BYTES)
{*p++ = '1';}
else
{return;}
pTimeStamp = (char *) &mm->timestampMsg;
for (j = 5; j >= 0; j--) {
*p++ = pTimeStamp[j];
}
*p++ = mm->signalLevel;
memcpy(p, mm->msg, msgLen);
Modes.rawOutUsed += (msgLen + 9);
if (Modes.rawOutUsed >= Modes.net_output_raw_size)
{
modesSendAllClients(Modes.ros, Modes.rawOut, Modes.rawOutUsed);
Modes.rawOutUsed = 0;
Modes.net_output_raw_rate_count = 0;
}
}
/* Write raw output to TCP clients. */
void modesSendRawOutput(struct modesMessage *mm) {
char *p = &Modes.rawOut[Modes.rawOutUsed];
int msgLen = mm->msgbits / 8;
int j;
unsigned char * pTimeStamp;
if (Modes.mlat) {
*p++ = '@';
pTimeStamp = (unsigned char *) &mm->timestampMsg;
for (j = 5; j >= 0; j--) {
sprintf(p, "%02X", pTimeStamp[j]);
p += 2;
}
Modes.rawOutUsed += 12; // additional 12 characters for timestamp
} else
*p++ = '*';
for (j = 0; j < msgLen; j++) {
sprintf(p, "%02X", mm->msg[j]);
p += 2;
}
*p++ = ';';
*p++ = '\n';
Modes.rawOutUsed += ((msgLen*2) + 3);
if (Modes.rawOutUsed >= Modes.net_output_raw_size)
{
modesSendAllClients(Modes.ros, Modes.rawOut, Modes.rawOutUsed);
Modes.rawOutUsed = 0;
Modes.net_output_raw_rate_count = 0;
}
}
//
// Write SBS output to TCP clients
// The message structure mm->bFlags tells us what has been updated by this message
//
void modesSendSBSOutput(struct modesMessage *mm) {
char msg[256], *p = msg;
uint32_t offset;
struct timeb epocTime;
struct tm stTime;
int msgType;
//
// SBS BS style output checked against the following reference
// http://www.homepages.mcb.net/bones/SBS/Article/Barebones42_Socket_Data.htm - seems comprehensive
//
// Decide on the basic SBS Message Type
if ((mm->msgtype == 0) || (mm->msgtype == 4) || (mm->msgtype == 20)) {
msgType = 5;
} else if ((mm->msgtype == 5) || (mm->msgtype == 21)) {
msgType = 6;
} else if (mm->msgtype == 16) {
msgType = 7;
} else if (mm->msgtype == 11) {
msgType = 8;
} else if (mm->msgtype != 17) {
return;
} else if (mm->metype == 4) {
msgType = 1;
} else if ((mm->metype >= 5) && (mm->metype <= 8)) {
msgType = 2;
} else if ((mm->metype >= 9) && (mm->metype <= 18)) {
msgType = 3;
} else if (mm->metype != 19) {
return;
} else if ((mm->mesub == 1) || (mm->mesub == 2)) {
msgType = 4;
} else {
return;
}
// Fields 1 to 6 : SBS message type and ICAO address of the aircraft and some other stuff
p += sprintf(p, "MSG,%d,111,11111,%06X,111111,", msgType, mm->addr);
// Fields 7 & 8 are the current time and date
if (mm->timestampMsg != (uint64_t)(-1)) { // Make sure the records' timestamp is valid before outputing it
epocTime = Modes.stSystemTimeBlk; // This is the time of the start of the Block we're processing
offset = (int) (mm->timestampMsg - Modes.timestampBlk); // This is the time (in 12Mhz ticks) into the Block
offset = offset / 12000; // convert to milliseconds
epocTime.millitm += offset; // add on the offset time to the Block start time
if (epocTime.millitm > 999) // if we've caused an overflow into the next second...
{epocTime.millitm -= 1000; epocTime.time ++;} // ..correct the overflow
stTime = *localtime(&epocTime.time); // convert the time to year, month day, hours, min, sec
p += sprintf(p, "%04d/%02d/%02d,", (stTime.tm_year+1900),(stTime.tm_mon+1), stTime.tm_mday);
p += sprintf(p, "%02d:%02d:%02d.%03d,", stTime.tm_hour, stTime.tm_min, stTime.tm_sec, epocTime.millitm);
} else {
p += sprintf(p, ",,");
}
// Fields 9 & 10 are the current time and date
ftime(&epocTime); // get the current system time & date
stTime = *localtime(&epocTime.time); // convert the time to year, month day, hours, min, sec
p += sprintf(p, "%04d/%02d/%02d,", (stTime.tm_year+1900),(stTime.tm_mon+1), stTime.tm_mday);
p += sprintf(p, "%02d:%02d:%02d.%03d", stTime.tm_hour, stTime.tm_min, stTime.tm_sec, epocTime.millitm);
// Field 11 is the callsign (if we have it)
if (mm->bFlags & MODES_ACFLAGS_CALLSIGN_VALID) {p += sprintf(p, ",%s", mm->flight);}
else {p += sprintf(p, ",");}
// Field 12 is the altitude (if we have it) - force to zero if we're on the ground
if ((mm->bFlags & MODES_ACFLAGS_AOG_GROUND) == MODES_ACFLAGS_AOG_GROUND) {
p += sprintf(p, ",0");
} else if (mm->bFlags & MODES_ACFLAGS_ALTITUDE_VALID) {
p += sprintf(p, ",%d", mm->altitude);
} else {
p += sprintf(p, ",");
}
// Field 13 and 14 are the ground Speed and Heading (if we have them)
if (mm->bFlags & MODES_ACFLAGS_NSEWSPD_VALID) {p += sprintf(p, ",%d,%d", mm->velocity, mm->heading);}
else {p += sprintf(p, ",,");}
// Fields 15 and 16 are the Lat/Lon (if we have it)
if (mm->bFlags & MODES_ACFLAGS_LATLON_VALID) {p += sprintf(p, ",%1.5f,%1.5f", mm->fLat, mm->fLon);}
else {p += sprintf(p, ",,");}
// Field 17 is the VerticalRate (if we have it)
if (mm->bFlags & MODES_ACFLAGS_VERTRATE_VALID) {p += sprintf(p, ",%d", mm->vert_rate);}
else {p += sprintf(p, ",");}
// Field 18 is the Squawk (if we have it)
if (mm->bFlags & MODES_ACFLAGS_SQUAWK_VALID) {p += sprintf(p, ",%x", mm->modeA);}
else {p += sprintf(p, ",");}
// Field 19 is the Squawk Changing Alert flag (if we have it)
if (mm->bFlags & MODES_ACFLAGS_FS_VALID) {
if ((mm->fs >= 2) && (mm->fs <= 4)) {
p += sprintf(p, ",-1");
} else {
p += sprintf(p, ",0");
}
} else {
p += sprintf(p, ",");
}
// Field 20 is the Squawk Emergency flag (if we have it)
if (mm->bFlags & MODES_ACFLAGS_SQUAWK_VALID) {
if ((mm->modeA == 0x7500) || (mm->modeA == 0x7600) || (mm->modeA == 0x7700)) {
p += sprintf(p, ",-1");
} else {
p += sprintf(p, ",0");
}
} else {
p += sprintf(p, ",");
}
// Field 21 is the Squawk Ident flag (if we have it)
if (mm->bFlags & MODES_ACFLAGS_FS_VALID) {
if ((mm->fs >= 4) && (mm->fs <= 5)) {
p += sprintf(p, ",-1");
} else {
p += sprintf(p, ",0");
}
} else {
p += sprintf(p, ",");
}
// Field 22 is the OnTheGround flag (if we have it)
if (mm->bFlags & MODES_ACFLAGS_AOG_VALID) {
if (mm->bFlags & MODES_ACFLAGS_AOG) {
p += sprintf(p, ",-1");
} else {
p += sprintf(p, ",0");
}
} else {
p += sprintf(p, ",");
}
p += sprintf(p, "\r\n");
modesSendAllClients(Modes.sbsos, msg, p-msg);
}
/* Turn an hex digit into its 4 bit decimal value.
* Returns -1 if the digit is not in the 0-F range. */
int hexDigitVal(int c) {
c = tolower(c);
if (c >= '0' && c <= '9') return c-'0';
else if (c >= 'a' && c <= 'f') return c-'a'+10;
else return -1;
}
/* This function decodes a string representing a Mode S message in
* raw hex format like: *8D4B969699155600E87406F5B69F;
* The string is supposed to be at the start of the client buffer
* and null-terminated.
*
* The message is passed to the higher level layers, so it feeds
* the selected screen output, the network output and so forth.
*
* If the message looks invalid is silently discarded.
*
* The function always returns 0 (success) to the caller as there is
* no case where we want broken messages here to close the client
* connection. */
int decodeHexMessage(struct client *c) {
char *hex = c->buf;
int l = strlen(hex), j;
unsigned char msg[MODES_LONG_MSG_BYTES];
struct modesMessage mm;
memset(&mm, 0, sizeof(mm));
// Always mark the timestamp as invalid for packets received over the internet
// Mixing of data from two or more different receivers and publishing
// as coming from one would lead to corrupt mlat data
// Non timemarked internet data has indeterminate delay
mm.timestampMsg = -1;
mm.signalLevel = -1;
// Remove spaces on the left and on the right
while(l && isspace(hex[l-1])) {
hex[l-1] = '\0'; l--;
}
while(isspace(*hex)) {
hex++; l--;
}
// Turn the message into binary.
// Accept *-AVR raw @-AVR/BEAST timeS+raw %-AVR timeS+raw (CRC good) <-BEAST timeS+sigL+raw
// and some AVR recorer that we can understand
if (hex[l-1] != ';') {return (0);} // not complete - abort
switch(hex[0]) {
case '<': {
mm.signalLevel = (hexDigitVal(hex[13])<<4) | hexDigitVal(hex[14]);
hex += 15; l -= 16; // Skip <, timestamp and siglevel, and ;
break;}
case '@':
case '%':
case '#':
case '$': {
hex += 13; l -= 14; // Skip @,%,#,$, and timestamp, and ;
break;}
case '*':
case ':': {
hex++; l-=2; // Skip * and ;
break;}
default: {
return (0); // We don't know what this is, so abort
break;}
}
if ( (l < 4) || (l > MODES_LONG_MSG_BYTES*2) ) return (0); // Too short or long message... broken
for (j = 0; j < l; j += 2) {
int high = hexDigitVal(hex[j]);
int low = hexDigitVal(hex[j+1]);
if (high == -1 || low == -1) return 0;
msg[j/2] = (high << 4) | low;
}
if (l < 5) {decodeModeAMessage(&mm, ((msg[0] << 8) | msg[1]));} // ModeA or ModeC
else {decodeModesMessage(&mm, msg);}
useModesMessage(&mm);
return (0);
}
/* Return a description of planes in json. */
char *aircraftsToJson(int *len) {
time_t now = time(NULL);
struct aircraft *a = Modes.aircrafts;
int buflen = 1024; /* The initial buffer is incremented as needed. */
char *buf = (char *) malloc(buflen), *p = buf;
int l;
l = snprintf(p,buflen,"[\n");
p += l; buflen -= l;
while(a) {
int altitude = a->altitude, speed = a->speed;
int position = 0;
int track = 0;
/* Convert units to metric if --metric was specified. */
if (Modes.metric) {
altitude = (int) (altitude / 3.2828);
speed = (int) (speed * 1.852);
}
if (a->bFlags & MODES_ACFLAGS_LATLON_VALID) {
position = 1;
}
if (a->bFlags & MODES_ACFLAGS_HEADING_VALID) {
track = 1;
}
l = snprintf(p,buflen,
"{\"hex\":\"%06x\", \"squawk\":\"%04x\", \"flight\":\"%s\", \"lat\":%f, "
"\"lon\":%f, \"validposition\":%d, \"altitude\":%d, \"track\":%d, \"validtrack\":%d,"
"\"speed\":%d, \"messages\":%ld, \"seen\":%d},\n",
a->addr, a->modeA, a->flight, a->lat, a->lon, position, a->altitude, a->track, track,
a->speed, a->messages, (int)(now - a->seen));
p += l; buflen -= l;
/* Resize if needed. */
if (buflen < 256) {
int used = p-buf;
buflen += 1024; // Our increment.
buf = (char *) realloc(buf,used+buflen);
p = buf+used;
}
a = a->next;
}
/* Remove the final comma if any, and closes the json array. */
if (*(p-2) == ',') {
*(p-2) = '\n';
p--;
buflen++;
}
l = snprintf(p,buflen,"]\n");
p += l; buflen -= l;
*len = p-buf;
return buf;
}
#define MODES_CONTENT_TYPE_HTML "text/html;charset=utf-8"
#define MODES_CONTENT_TYPE_CSS "text/css;charset=utf-8"
#define MODES_CONTENT_TYPE_JSON "application/json;charset=utf-8"
#define MODES_CONTENT_TYPE_JS "application/javascript;charset=utf-8"
/* Get an HTTP request header and write the response to the client.
* Again here we assume that the socket buffer is enough without doing
* any kind of userspace buffering.
*
* Returns 1 on error to signal the caller the client connection should
* be closed. */
int handleHTTPRequest(struct client *c) {
char hdr[512];
int clen, hdrlen;
int httpver, keepalive;
char *p, *url, *content;
char ctype[48];
char getFile[1024];
char *ext;
if (Modes.debug & MODES_DEBUG_NET)
printf("\nHTTP request: %s\n", c->buf);
// Minimally parse the request.
httpver = (strstr(c->buf, "HTTP/1.1") != NULL) ? 11 : 10;
if (httpver == 10) {
// HTTP 1.0 defaults to close, unless otherwise specified.
keepalive = strstr(c->buf, "Connection: keep-alive") != NULL;
} else if (httpver == 11) {
// HTTP 1.1 defaults to keep-alive, unless close is specified.
keepalive = strstr(c->buf, "Connection: close") == NULL;
}
// Identify he URL.
p = strchr(c->buf,' ');
if (!p) return 1; /* There should be the method and a space... */
url = ++p; /* Now this should point to the requested URL. */
p = strchr(p, ' ');
if (!p) return 1; /* There should be a space before HTTP/... */
*p = '\0';
if (Modes.debug & MODES_DEBUG_NET) {
printf("\nHTTP keep alive: %d\n", keepalive);
printf("HTTP requested URL: %s\n\n", url);
}
if (strlen(url) < 2) {
snprintf(getFile, sizeof getFile, "./public_html/gmap.html"); // Default file
} else {
snprintf(getFile, sizeof getFile, "./public_html%s", url);
}
/* Select the content to send, we have just two so far:
* "/" -> Our google map application.
* "/data.json" -> Our ajax request to update planes. */
if (strstr(url, "/data.json")) {
content = aircraftsToJson(&clen);
//snprintf(ctype, sizeof ctype, MODES_CONTENT_TYPE_JSON);
} else {
struct stat sbuf;
int fd = -1;
if (stat(getFile, &sbuf) != -1 && (fd = open(getFile, O_RDONLY)) != -1) {
content = (char *) malloc(sbuf.st_size);
if (read(fd, content, sbuf.st_size) == -1) {
snprintf(content, sbuf.st_size, "Error reading from file: %s", strerror(errno));
}
clen = sbuf.st_size;
} else {
char buf[128];
clen = snprintf(buf,sizeof(buf),"Error opening HTML file: %s", strerror(errno));
content = strdup(buf);
}
if (fd != -1) {
close(fd);
}
}
// Get file extension and content type
snprintf(ctype, sizeof ctype, MODES_CONTENT_TYPE_HTML); // Default content type
ext = strrchr(getFile, '.');
if (strlen(ext) > 0) {
if (strstr(ext, ".json")) {
snprintf(ctype, sizeof ctype, MODES_CONTENT_TYPE_JSON);
} else if (strstr(ext, ".css")) {
snprintf(ctype, sizeof ctype, MODES_CONTENT_TYPE_CSS);
} else if (strstr(ext, ".js")) {
snprintf(ctype, sizeof ctype, MODES_CONTENT_TYPE_JS);
}
}
/* Create the header and send the reply. */
hdrlen = snprintf(hdr, sizeof(hdr),
"HTTP/1.1 200 OK\r\n"
"Server: Dump1090\r\n"
"Content-Type: %s\r\n"
"Connection: %s\r\n"
"Content-Length: %d\r\n"
"\r\n",
ctype,
keepalive ? "keep-alive" : "close",
clen);
if (Modes.debug & MODES_DEBUG_NET) {
printf("HTTP Reply header:\n%s", hdr);
}
// Send header and content.
if (write(c->fd, hdr, hdrlen) == -1 || write(c->fd, content, clen) == -1) {
free(content);
return 1;
}
free(content);
Modes.stat_http_requests++;
return !keepalive;
}
/* This function polls the clients using read() in order to receive new
* messages from the net.
*
* The message is supposed to be separated by the next message by the
* separator 'sep', that is a null-terminated C string.
*
* Every full message received is decoded and passed to the higher layers
* calling the function 'handler'.
*
* The handelr returns 0 on success, or 1 to signal this function we
* should close the connection with the client in case of non-recoverable
* errors. */
void modesReadFromClient(struct client *c, char *sep,
int(*handler)(struct client *))
{
while(1) {
int left = MODES_CLIENT_BUF_SIZE - c->buflen;
int nread = read(c->fd, c->buf+c->buflen, left);
int fullmsg = 0;
int i;
char *p;
if (nread <= 0) {
if (nread == 0 || errno != EAGAIN) {
/* Error, or end of file. */
modesFreeClient(c->fd);
}
break; /* Serve next client. */
}
c->buflen += nread;
/* Always null-term so we are free to use strstr() */
c->buf[c->buflen] = '\0';
/* If there is a complete message there must be the separator 'sep'
* in the buffer, note that we full-scan the buffer at every read
* for simplicity. */
while ((p = strstr(c->buf, sep)) != NULL) {
i = p - c->buf; /* Turn it as an index inside the buffer. */
c->buf[i] = '\0'; /* Te handler expects null terminated strings. */
/* Call the function to process the message. It returns 1
* on error to signal we should close the client connection. */
if (handler(c)) {
modesFreeClient(c->fd);
return;
}
/* Move what's left at the start of the buffer. */
i += strlen(sep); /* The separator is part of the previous msg. */
memmove(c->buf,c->buf+i,c->buflen-i);
c->buflen -= i;
c->buf[c->buflen] = '\0';
/* Maybe there are more messages inside the buffer.
* Start looping from the start again. */
fullmsg = 1;
}
/* If our buffer is full discard it, this is some badly
* formatted shit. */
if (c->buflen == MODES_CLIENT_BUF_SIZE) {
c->buflen = 0;
/* If there is garbage, read more to discard it ASAP. */
continue;
}
/* If no message was decoded process the next client, otherwise
* read more data from the same client. */
if (!fullmsg) break;
}
}
/* Read data from clients. This function actually delegates a lower-level
* function that depends on the kind of service (raw, http, ...). */
void modesReadFromClients(void) {
int j;
struct client *c;
for (j = 0; j <= Modes.maxfd; j++) {
if ((c = Modes.clients[j]) == NULL) continue;
if (c->service == Modes.ris)
modesReadFromClient(c,"\n",decodeHexMessage);
else if (c->service == Modes.https)
modesReadFromClient(c,"\r\n\r\n",handleHTTPRequest);
}
}
/* ================================ Main ==================================== */
void showHelp(void) {
printf(
"-----------------------------------------------------------------------------\n"
"| dump1090 ModeS Receiver Ver : " MODES_DUMP1090_VERSION " |\n"
"-----------------------------------------------------------------------------\n"
"--device-index <index> Select RTL device (default: 0)\n"
"--gain <db> Set gain (default: max gain. Use -100 for auto-gain)\n"
"--enable-agc Enable the Automatic Gain Control (default: off)\n"
"--freq <hz> Set frequency (default: 1090 Mhz)\n"
"--ifile <filename> Read data from file (use '-' for stdin)\n"
"--interactive Interactive mode refreshing data on screen\n"
"--interactive-rows <num> Max number of rows in interactive mode (default: 15)\n"
"--interactive-ttl <sec> Remove from list if idle for <sec> (default: 60)\n"
"--interactive-rtl1090 Display flight table in RTL1090 format\n"
"--raw Show only messages hex values\n"
"--net Enable networking\n"
"--modeac Enable decoding of SSR Modes 3/A & 3/C\n"
"--net-beast TCP raw output in Beast binary format\n"
"--net-only Enable just networking, no RTL device or file used\n"
"--net-ro-size <size> TCP raw output minimum size (default: 0)\n"
"--net-ro-rate <rate> TCP raw output memory flush rate (default: 0)\n"
"--net-ro-port <port> TCP raw output listen port (default: 30002)\n"
"--net-ri-port <port> TCP raw input listen port (default: 30001)\n"
"--net-http-port <port> HTTP server port (default: 8080)\n"
"--net-sbs-port <port> TCP BaseStation output listen port (default: 30003)\n"
"--lat <latitude> Reference/receiver latitide for surface posn (opt)\n"
"--lon <longitude> Reference/receiver longitude for surface posn (opt)\n"
"--fix Enable single-bits error correction using CRC\n"
"--no-fix Disable single-bits error correction using CRC\n"
"--no-crc-check Disable messages with broken CRC (discouraged)\n"
"--aggressive More CPU for more messages (two bits fixes, ...)\n"
"--mlat display raw messages in Beast ascii mode\n"
"--stats With --ifile print stats at exit. No other output\n"
"--onlyaddr Show only ICAO addresses (testing purposes)\n"
"--metric Use metric units (meters, km/h, ...)\n"
"--snip <level> Strip IQ file removing samples < level\n"
"--debug <flags> Debug mode (verbose), see README for details\n"
"--quiet Disable output to stdout. Use for daemon applications\n"
"--ppm <error> Set receiver error in parts per million (default 0)\n"
"--help Show this help\n"
"\n"
"Debug mode flags: d = Log frames decoded with errors\n"
" D = Log frames decoded with zero errors\n"
" c = Log frames with bad CRC\n"
" C = Log frames with good CRC\n"
" p = Log frames with bad preamble\n"
" n = Log network debugging info\n"
" j = Log frames to frames.js, loadable by debug.html\n"
);
}
/* This function is called a few times every second by main in order to
* perform tasks we need to do continuously, like accepting new clients
* from the net, refreshing the screen in interactive mode, and so forth. */
void backgroundTasks(void) {
if (Modes.net) {
modesAcceptClients();
modesReadFromClients();
}
// If Modes.aircrafts is not NULL, remove any stale aircraft
if (Modes.aircrafts)
{interactiveRemoveStaleAircrafts();}
// Refresh screen when in interactive mode
if ((Modes.interactive) &&
((mstime() - Modes.interactive_last_update) > MODES_INTERACTIVE_REFRESH_TIME) ) {
// Attempt to reconsile any ModeA/C with known Mode-S
// We can't condition on Modes.modeac because ModeA/C could be comming
// in from a raw input port which we can't turn off.
interactiveUpdateAircraftModeS();
// Now display Mode-S and any non-reconsiled Modes-A/C
interactiveShowData();
Modes.interactive_last_update = mstime();
}
}
int main(int argc, char **argv) {
int j;
// Set sane defaults
modesInitConfig();
signal(SIGINT, sigintHandler); // Define Ctrl/C handler (exit program)
/* Parse the command line options */
for (j = 1; j < argc; j++) {
int more = j+1 < argc; /* There are more arguments. */
if (!strcmp(argv[j],"--device-index") && more) {
Modes.dev_index = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--gain") && more) {
Modes.gain = (int) atof(argv[++j])*10; /* Gain is in tens of DBs */
} else if (!strcmp(argv[j],"--enable-agc")) {
Modes.enable_agc++;
} else if (!strcmp(argv[j],"--freq") && more) {
Modes.freq = (int) strtoll(argv[++j],NULL,10);
} else if (!strcmp(argv[j],"--ifile") && more) {
Modes.filename = strdup(argv[++j]);
} else if (!strcmp(argv[j],"--fix")) {
Modes.fix_errors = 1;
} else if (!strcmp(argv[j],"--no-fix")) {
Modes.fix_errors = 0;
Modes.aggressive = 0;
} else if (!strcmp(argv[j],"--no-crc-check")) {
Modes.check_crc = 0;
} else if (!strcmp(argv[j],"--raw")) {
Modes.raw = 1;
} else if (!strcmp(argv[j],"--net")) {
Modes.net = 1;
} else if (!strcmp(argv[j],"--modeac")) {
Modes.mode_ac = 1;
} else if (!strcmp(argv[j],"--net-beast")) {
Modes.beast = 1;
} else if (!strcmp(argv[j],"--net-only")) {
Modes.net = 1;
Modes.net_only = 1;
} else if (!strcmp(argv[j],"--net-ro-size") && more) {
Modes.net_output_raw_size = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--net-ro-rate") && more) {
Modes.net_output_raw_rate = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--net-ro-port") && more) {
Modes.net_output_raw_port = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--net-ri-port") && more) {
Modes.net_input_raw_port = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--net-http-port") && more) {
Modes.net_http_port = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--net-sbs-port") && more) {
Modes.net_output_sbs_port = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--onlyaddr")) {
Modes.onlyaddr = 1;
} else if (!strcmp(argv[j],"--metric")) {
Modes.metric = 1;
} else if (!strcmp(argv[j],"--aggressive")) {
Modes.aggressive = 1;
Modes.fix_errors = 1;
} else if (!strcmp(argv[j],"--interactive")) {
Modes.interactive = 1;
} else if (!strcmp(argv[j],"--interactive-rows") && more) {
Modes.interactive_rows = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--interactive-ttl") && more) {
Modes.interactive_ttl = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--lat") && more) {
Modes.fUserLat = atof(argv[++j]);
} else if (!strcmp(argv[j],"--lon") && more) {
Modes.fUserLon = atof(argv[++j]);
} else if (!strcmp(argv[j],"--debug") && more) {
char *f = argv[++j];
while(*f) {
switch(*f) {
case 'D': Modes.debug |= MODES_DEBUG_DEMOD; break;
case 'd': Modes.debug |= MODES_DEBUG_DEMODERR; break;
case 'C': Modes.debug |= MODES_DEBUG_GOODCRC; break;
case 'c': Modes.debug |= MODES_DEBUG_BADCRC; break;
case 'p': Modes.debug |= MODES_DEBUG_NOPREAMBLE; break;
case 'n': Modes.debug |= MODES_DEBUG_NET; break;
case 'j': Modes.debug |= MODES_DEBUG_JS; break;
default:
fprintf(stderr, "Unknown debugging flag: %c\n", *f);
exit(1);
break;
}
f++;
}
} else if (!strcmp(argv[j],"--stats")) {
Modes.stats = 1;
} else if (!strcmp(argv[j],"--snip") && more) {
snipMode(atoi(argv[++j]));
exit(0);
} else if (!strcmp(argv[j],"--help")) {
showHelp();
exit(0);
} else if (!strcmp(argv[j],"--ppm") && more) {
Modes.ppm_error = atoi(argv[++j]);
} else if (!strcmp(argv[j],"--quiet")) {
Modes.quiet = 1;
} else if (!strcmp(argv[j],"--mlat")) {
Modes.mlat = 1;
} else if (!strcmp(argv[j],"--interactive-rtl1090")) {
Modes.interactive = 1;
Modes.interactive_rtl1090 = 1;
} else {
fprintf(stderr,
"Unknown or not enough arguments for option '%s'.\n\n",
argv[j]);
showHelp();
exit(1);
}
}
// Initialization
modesInit();
if (Modes.debug & MODES_DEBUG_BADCRC) {
testAndTimeBitCorrection();
}
if (Modes.net_only) {
fprintf(stderr,"Net-only mode, no RTL device or file open.\n");
} else if (Modes.filename == NULL) {
modesInitRTLSDR();
} else {
if (Modes.filename[0] == '-' && Modes.filename[1] == '\0') {
Modes.fd = STDIN_FILENO;
} else if ((Modes.fd = open(Modes.filename,O_RDONLY)) == -1) {
perror("Opening data file");
exit(1);
}
}
if (Modes.net) modesInitNet();
/* If the user specifies --net-only, just run in order to serve network
* clients without reading data from the RTL device. */
while (Modes.net_only) {
if (Modes.exit) exit(0); // If we exit net_only nothing further in main()
backgroundTasks();
usleep(100000);
}
/* Create the thread that will read the data from the device. */
pthread_create(&Modes.reader_thread, NULL, readerThreadEntryPoint, NULL);
pthread_mutex_lock(&Modes.data_mutex);
while(1) {
if (!Modes.data_ready) {
pthread_cond_wait(&Modes.data_cond,&Modes.data_mutex);
continue;
}
computeMagnitudeVector();
Modes.stSystemTimeBlk = Modes.stSystemTimeRTL;
/* Signal to the other thread that we processed the available data
* and we want more (useful for --ifile). */
Modes.data_ready = 0;
pthread_cond_signal(&Modes.data_cond);
/* Process data after releasing the lock, so that the capturing
* thread can read data while we perform computationally expensive
* stuff * at the same time. (This should only be useful with very
* slow processors). */
pthread_mutex_unlock(&Modes.data_mutex);
detectModeS(Modes.magnitude, MODES_ASYNC_BUF_SAMPLES);
Modes.timestampBlk += (MODES_ASYNC_BUF_SAMPLES*6);
backgroundTasks();
pthread_mutex_lock(&Modes.data_mutex);
if (Modes.exit) break;
}
// If --stats were given, print statistics
if (Modes.stats) {
printf("\n\n");
printf("%d ModeA/C detected\n", Modes.stat_ModeAC);
printf("%d valid preambles\n", Modes.stat_valid_preamble);
printf("%d DF-?? fields corrected for length\n", Modes.stat_DF_Len_Corrected);
printf("%d DF-?? fields corrected for type\n", Modes.stat_DF_Type_Corrected);
printf("%d demodulated again after phase correction\n", Modes.stat_out_of_phase);
printf("%d demodulated with zero errors\n", Modes.stat_demodulated);
printf("%d with good crc\n", Modes.stat_goodcrc);
printf("%d with bad crc\n", Modes.stat_badcrc);
printf("%d errors corrected\n", Modes.stat_fixed);
printf("%d single bit errors\n", Modes.stat_single_bit_fix);
printf("%d two bits errors\n", Modes.stat_two_bits_fix);
printf("%d total usable messages\n", Modes.stat_goodcrc + Modes.stat_fixed);
}
rtlsdr_cancel_async(Modes.dev); // Cancel rtlsdr_read_async will cause data input thread to terminate cleanly
rtlsdr_close(Modes.dev);
exit (0);
}
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