/* dump1090, a Mode S messages decoder for RTLSDR devices. * * Copyright (C) 2012 by Salvatore Sanfilippo * * 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #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 "1.04.0905.13" #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_SBS_LAT_LONG_FRESH (1<<0) #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 computed from EW and NS components 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 sbsflags; 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 */ /* 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 errorbit; // Bit corrected. -1 if no bit 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_is_valid; int heading; int fflag; // 1 = Odd, 0 = Even CPR message. int tflag; // UTC synchronized? int raw_latitude; // Non decoded latitude. int raw_longitude; // Non decoded longitude. char flight[16]; // 8 chars flight number. int ew_dir; // 0 = East, 1 = West. int ew_velocity; // E/W velocity. int ns_dir; // 0 = North, 1 = South. int ns_velocity; // N/S velocity. int vert_rate_source; // Vertical rate source. int vert_rate_sign; // Vertical rate sign. int vert_rate; // Vertical rate. int velocity; // Computed from EW and NS velocity. // DF4, DF5, DF20, DF21 int fs; // Flight status for DF4,5,20,21 int dr; // Request extraction of downlink request. int um; // Request extraction of downlink request. int modeA; // 13 bits identity (Squawk). // Fields used by multiple message types. int altitude, unit; }; 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, struct aircraft *a); void useModesMessage(struct modesMessage *mm); int fixSingleBitErrors(unsigned char *msg, int bits); int fixTwoBitsErrors(unsigned char *msg, int bits); 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; } 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); // 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); } } } /* =============================== 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, fix1 = -1, fix2 = -1; if (fixable != -1) { fix1 = fixable & 0xff; if (fixable > 255) fix2 = fixable >> 8; } 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,"], \"fix1\": %d, \"fix2\": %d, \"bits\": %d, \"hex\": \"", fix1, fix2, 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 = -1; if (msgtype == 17) { fixable = fixSingleBitErrors(msg, MODES_LONG_MSG_BITS); if (fixable == -1) fixable = fixTwoBitsErrors(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);} 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; // 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->errorbit = -1; } /* ===================== 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); } /* 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 Q if (ID13Field & 0x0020) {hexGillham |= 0x0100;} // Bit 5 = B1 if (ID13Field & 0x0010) {hexGillham |= 0x0001;} // Bit 4 = D1 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 AC13Field &= 0x1FFF; // limit the field to 13 bits 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 AC12Field &= 0x0FFF; // limit the field to 12 bits *unit = MODES_UNIT_FEET; if (q_bit) { /// N is the 11 bit integer resulting from the removal of bit Q int n = ((AC12Field & 0x0FE0) >> 1) | (AC12Field & 0x000F); // The final altitude is the resulting number multiplied by 25, minus 1000. return ((n * 25) - 1000); } else { // N is an 11 bit Gillham coded altitude int n = n = ModeAToModeC(decodeID13Field(AC12Field)); if (n < -12) {n = 0;} return (100 * n); } } /* 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->errorbit = -1; // 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->errorbit = fixSingleBitErrors(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 (-1 != mm->errorbit) { // 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 DF4,5,20,21 mm->ca = // Responder capabilities mm->fs = msg[0] & 7; // Flight status for DF4,5,20,21 mm->dr = (msg[1] >> 3) & 0x1F; // Request extraction of downlink request mm->um = ((msg[1] & 7) << 3) | (msg[2] >> 5); // Request extraction of downlink request // Fields for DF5, DF21 = Gillham encoded Squawk if (mm->msgtype == 5 || mm->msgtype == 21) { mm->modeA = decodeID13Field((msg[2] << 8) | msg[3]); } // Fields for DF0, DF4, DF16, DF20 13 bit altitude if (mm->msgtype == 0 || mm->msgtype == 4 || mm->msgtype == 16 || mm->msgtype == 20) { mm->altitude = decodeAC13Field(((msg[2] << 8) | msg[3]), &mm->unit); } // Fields for DF17 squitter if (mm->msgtype == 17) { mm->metype = msg[4] >> 3; // Extended squitter message type mm->mesub = msg[4] & 7; // Extended squitter message subtype // Decode the extended squitter message if (mm->metype >= 1 && mm->metype <= 4) { // Aircraft Identification and Category uint32_t chars; 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 (mm->metype >= 9 && mm->metype <= 18) { // Airborne position Message mm->fflag = msg[6] & (1<<2); mm->tflag = msg[6] & (1<<3); mm->altitude = decodeAC12Field(((msg[5] << 4) | (msg[6] >> 4)), &mm->unit); 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]); } else if (mm->metype == 19) { // Airborne Velocity Message if (mm->mesub == 1 || mm->mesub == 2) { mm->ew_dir = (msg[5]&4) >> 2; mm->ew_velocity = ((msg[5]&3) << 8) | msg[6]; mm->ns_dir = (msg[7]&0x80) >> 7; mm->ns_velocity = ((msg[7]&0x7f) << 3) | ((msg[8]&0xe0) >> 5); mm->vert_rate_source = (msg[8]&0x10) >> 4; mm->vert_rate_sign = (msg[8]&0x8) >> 3; mm->vert_rate = ((msg[8]&7) << 6) | ((msg[9]&0xfc) >> 2); // Compute velocity and angle from the two speed components mm->velocity = (int) sqrt(mm->ns_velocity*mm->ns_velocity + mm->ew_velocity*mm->ew_velocity); if (mm->velocity) { int ewv = mm->ew_velocity; int nsv = mm->ns_velocity; double heading; if (mm->ew_dir) ewv *= -1; if (mm->ns_dir) nsv *= -1; heading = atan2(ewv,nsv); // Convert to degrees mm->heading = (int) (heading * 360 / (M_PI*2)); // We don't want negative values but a 0-360 scale if (mm->heading < 0) mm->heading += 360; } else { mm->heading = 0; } } else if (mm->mesub == 3 || mm->mesub == 4) { mm->heading_is_valid = msg[5] & (1<<2); mm->heading = (int) (360.0/128) * (((msg[5] & 3) << 5) | (msg[6] >> 3)); } } } // Fields for DF20, DF21 Comm-B if ((mm->msgtype == 20) || (mm->msgtype == 21)){ if (msg[4] == 0x20) { // Aircraft Identification uint32_t chars; 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; char * pTimeStamp; // Handle only addresses mode first. if (Modes.onlyaddr) { printf("%06x\n", mm->addr); return; } // Show the raw message. if (Modes.mlat) { printf("@"); pTimeStamp = (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->errorbit != -1) printf("Single bit error fixed, bit %d\n", mm->errorbit); 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->dr); printf(" UM : %d\n", mm->um); 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->dr); printf(" UM : %d\n", mm->um); 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 : %s\n", 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->fflag ? "odd" : "even"); printf(" T flag : %s\n", mm->tflag ? "UTC" : "non-UTC"); printf(" Altitude : %d feet\n", mm->altitude); 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 direction : %d\n", mm->ew_dir); printf(" EW velocity : %d\n", mm->ew_velocity); printf(" NS direction : %d\n", mm->ns_dir); printf(" NS velocity : %d\n", mm->ns_velocity); printf(" Vertical rate src : %d\n", mm->vert_rate_source); printf(" Vertical rate sign: %d\n", mm->vert_rate_sign); printf(" Vertical rate : %d\n", mm->vert_rate); } else if (mm->mesub == 3 || mm->mesub == 4) { printf(" Heading status: %d", mm->heading_is_valid); printf(" Heading: %d", mm->heading); } 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 { int modeC = ModeAToModeC(mm->modeA); printf(" Mode A : %04x\n", mm->modeA); if (modeC >= -13) {printf(" Mode C : %d feet\n", (modeC * 100));} } } else { printf("DF %d: Unknown DF Format.\n", mm->msgtype); } } /* 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; // 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.errorbit == -1) { if (mm.crcok) {Modes.stat_goodcrc++;} else {Modes.stat_badcrc++;} } else { Modes.stat_badcrc++; Modes.stat_fixed++; if (mm.errorbit < MODES_LONG_MSG_BITS) {Modes.stat_single_bit_fix++;} else {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.errorbit != -1)) dumpRawMessage("Decoded with bad CRC", msg, m, j); else if (Modes.debug & MODES_DEBUG_GOODCRC && mm.crcok && mm.errorbit == -1) 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.stats && (Modes.check_crc == 0 || mm->crcok)) { // Track aircrafts if... if ( (Modes.interactive) // in interactive mode || (Modes.stat_http_requests > 0) // or if the HTTP interface is enabled || (Modes.stat_sbs_connections > 0) // or if sbs connections are established || (Modes.mode_ac) ) { // or if mode A/C decoding is enabled struct aircraft *a = interactiveReceiveData(mm); if ( (a) && (mm->msgtype < 32) // don't even try to send ModesA/C to SBS clients && (Modes.stat_sbs_connections > 0) ) {modesSendSBSOutput(mm, a);} // Feed SBS output clients } // In non-interactive mode, and non-quiet mode, display messages on // standard output as they occur. if (!Modes.interactive && !Modes.quiet) { displayModesMessage(mm); if (!Modes.raw && !Modes.onlyaddr) printf("\n"); } // 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; memset(a->signalLevel, mm->signalLevel, 8); // First time, initialise everything // to the first signal strength a->lat = 0.0; a->lon = 0.0; // 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) { a->modeACflags = MODEAC_MSG_FLAG; a->modeA = mm->modeA; a->modeC = ModeAToModeC(mm->modeA | mm->fs); a->altitude = a->modeC * 100; if (a->modeC < -12) {a->modeACflags |= MODEAC_MSG_MODEA_ONLY;} } 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 // First 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 } // Next 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 (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 (a->lon > 180) a->lon -= 360; a->seenLatLon = a->seen; a->timestampLatLon = a->timestamp; a->sbsflags |= MODES_SBS_LAT_LONG_FRESH; } /* 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 latr, double lonr) { double AirDlat; double AirDlon; double lat; double lon; double rlon, rlat; int j,m; // If not passed a lat/long, we must be using aircraft relative if ( (latr == 0) && (lonr == 0) ) { latr = a->lat; lonr = a->lon; } if ( (latr == 0) && (lonr == 0) ) 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->lat = a->lon = 0; // 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->lat = a->lon = 0; // 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->sbsflags |= MODES_SBS_LAT_LONG_FRESH; 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 (mm->msgtype == 0 || mm->msgtype == 4 || mm->msgtype == 20) { 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 ((mm->msgtype == 20) && (mm->msg[4] == 0x20)) { memcpy(a->flight, mm->flight, sizeof(a->flight)); } } else if(mm->msgtype == 5 || mm->msgtype == 21) { 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 ((mm->msgtype == 21) && (mm->msg[4] == 0x20)) { memcpy(a->flight, mm->flight, sizeof(a->flight)); } } else if (mm->msgtype == 17) { if (mm->metype >= 1 && mm->metype <= 4) { memcpy(a->flight, mm->flight, sizeof(a->flight)); } else if (mm->metype >= 9 && mm->metype <= 18) { 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 (mm->fflag) { a->odd_cprlat = mm->raw_latitude; a->odd_cprlon = mm->raw_longitude; a->odd_cprtime = mstime(); } else { a->even_cprlat = mm->raw_latitude; a->even_cprlon = mm->raw_longitude; a->even_cprtime = mstime(); } // Try relative CPR first if (decodeCPRrelative(a, mm->fflag, 0, 0, 0)) { // If it fails then try global if the two data are less than 10 seconds apart, compute // the position. if (abs((int)(a->even_cprtime - a->odd_cprtime)) <= 10000) { decodeCPR(a, mm->fflag, 0); } } } else if (mm->metype == 19) { if (mm->mesub == 1 || mm->mesub == 2) { a->speed = mm->velocity; a->track = mm->heading; } } } else 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 squawk[5] = " "; // Convert units to metric if --metric was specified if (Modes.metric) { altitude = (int) (altitude / 3.2828); speed = (int) (speed * 1.852); } if (altitude > 99999) { altitude = 99999; } else if (altitude == -999900) { altitude = 0; } else if (altitude < -9999) { altitude = -9999; } if (a->modeA) { sprintf(squawk, "%04x", a->modeA); } if (msgs > 99999) { msgs = 99999; } if (Modes.interactive_rtl1090 != 0) { char fl[5] = " "; char tt[5] = " "; char gs[5] = " "; if (altitude > 0) { sprintf(fl,"F%03d",(altitude/100)); } if (speed > 0) { sprintf (gs,"%3d",speed); } if (a->track > 0) { sprintf (tt,"%03d",a->track); } printf("%06x %-8s %-4s %-3s %-3s %4s %-6d %-2d\n", a->addr, a->flight, fl, gs, tt, squawk, msgs, (int)(now - a->seen)); } else { char mode[5] = " \0"; 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) { mode[0] = 'S'; } else if (flags & MODEAC_MSG_MODEA_ONLY) { mode[0] = 'A'; } if (flags & MODEAC_MSG_MODEA_HIT) {mode[2] = 'a';} if (flags & MODEAC_MSG_MODEC_HIT) {mode[3] = 'c';} printf("%06x %-4s %-4s %-8s %5d %3d %3d %7.03f %8.03f %3d %5d %2d\n", a->addr, mode, squawk, a->flight, altitude, speed, a->track, a->lat, a->lon, 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; char * pTimeStamp; if (Modes.mlat) { *p++ = '@'; pTimeStamp = (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. */ void modesSendSBSOutput(struct modesMessage *mm, struct aircraft *a) { char msg[256], *p = msg; char strCommon[128], *pCommon = strCommon; int emergency = 0, ground = 0, alert = 0, spi = 0; uint32_t offset; struct timeb epocTime; struct tm stTime; if (mm->msgtype == 4 || mm->msgtype == 5 || mm->msgtype == 21) { if (mm->modeA == 0x7500 || mm->modeA == 0x7600 || mm->modeA == 0x7700) emergency = -1; if (mm->fs == 1 || mm->fs == 3) ground = -1; if (mm->fs == 2 || mm->fs == 3 || mm->fs == 4) alert = -1; if (mm->fs == 4 || mm->fs == 5) spi = -1; } // ICAO address of the aircraft pCommon += sprintf(pCommon, "111,11111,%06X,111111,", mm->addr); // Make sure the records' timestamp is valid before outputing it if (mm->timestampMsg != (uint64_t)(-1)) { // Do the records' time and date now 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 pCommon += sprintf(pCommon, "%04d/%02d/%02d,", (stTime.tm_year+1900),(stTime.tm_mon+1), stTime.tm_mday); pCommon += sprintf(pCommon, "%02d:%02d:%02d.%03d,", stTime.tm_hour, stTime.tm_min, stTime.tm_sec, epocTime.millitm); } else { pCommon += sprintf(pCommon, ",,"); } // Do the current time and date now ftime(&epocTime); // get the current system time & date stTime = *localtime(&epocTime.time); // convert the time to year, month day, hours, min, sec pCommon += sprintf(pCommon, "%04d/%02d/%02d,", (stTime.tm_year+1900),(stTime.tm_mon+1), stTime.tm_mday); pCommon += sprintf(pCommon, "%02d:%02d:%02d.%03d", stTime.tm_hour, stTime.tm_min, stTime.tm_sec, epocTime.millitm); if (mm->msgtype == 0) { p += sprintf(p, "MSG,5,%s,,%d,,,,,,,,,,", strCommon, mm->altitude); } else if (mm->msgtype == 4) { p += sprintf(p, "MSG,5,%s,,%d,,,,,,,%d,%d,%d,%d", strCommon, mm->altitude, alert, emergency, spi, ground); } else if (mm->msgtype == 5) { p += sprintf(p, "MSG,6,%s,,,,,,,,%x,%d,%d,%d,%d", strCommon, mm->modeA, alert, emergency, spi, ground); } else if (mm->msgtype == 11) { p += sprintf(p, "MSG,8,%s,,,,,,,,,,,,", strCommon); } else if (mm->msgtype == 17 && mm->metype == 4) { p += sprintf(p, "MSG,1,%s,%s,,,,,,,,0,0,0,0", strCommon, mm->flight); } else if (mm->msgtype == 17 && mm->metype >= 9 && mm->metype <= 18) { if ( ((a->lat == 0) && (a->lon == 0)) || ((a->sbsflags & MODES_SBS_LAT_LONG_FRESH) == 0) ){ p += sprintf(p, "MSG,3,%s,,%d,,,,,,,0,0,0,0", strCommon, mm->altitude); } else { p += sprintf(p, "MSG,3,%s,,%d,,,%1.5f,%1.5f,,,0,0,0,0", strCommon, mm->altitude, a->lat, a->lon); a->sbsflags &= ~MODES_SBS_LAT_LONG_FRESH; } } else if (mm->msgtype == 17 && mm->metype == 19 && mm->mesub == 1) { int vr = (mm->vert_rate_sign==0?1:-1) * (mm->vert_rate-1) * 64; p += sprintf(p, "MSG,4,%s,,,%d,%d,,,%i,,0,0,0,0", strCommon, mm->velocity, mm->heading, vr); } else if (mm->msgtype == 21) { p += sprintf(p, "MSG,6,%s,,,,,,,,%x,%d,%d,%d,%d", strCommon, mm->modeA, alert, emergency, spi, ground); } else { return; } *p++ = '\r'; *p++ = '\n'; // or just ?? 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; // 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; /* Convert units to metric if --metric was specified. */ if (Modes.metric) { altitude = (int) (altitude / 3.2828); speed = (int) (speed * 1.852); } l = snprintf(p,buflen, "{\"hex\":\"%06x\", \"squawk\":\"%04x\", \"flight\":\"%s\", \"lat\":%f, " "\"lon\":%f, \"altitude\":%d, \"track\":%d, " "\"speed\":%d, \"messages\":%ld, \"seen\":%d},\n", a->addr, a->modeA, a->flight, a->lat, a->lon, a->altitude, a->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 Select RTL device (default: 0)\n" "--gain Set gain (default: max gain. Use -100 for auto-gain)\n" "--enable-agc Enable the Automatic Gain Control (default: off)\n" "--freq Set frequency (default: 1090 Mhz)\n" "--ifile Read data from file (use '-' for stdin)\n" "--interactive Interactive mode refreshing data on screen\n" "--interactive-rows Max number of rows in interactive mode (default: 15)\n" "--interactive-ttl Remove from list if idle for (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 TCP raw output minimum size (default: 0)\n" "--net-ro-rate TCP raw output memory flush rate (default: 0)\n" "--net-ro-port TCP raw output listen port (default: 30002)\n" "--net-ri-port TCP raw input listen port (default: 30001)\n" "--net-http-port HTTP server port (default: 8080)\n" "--net-sbs-port TCP BaseStation output listen port (default: 30003)\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 Strip IQ file removing samples < level\n" "--debug Debug mode (verbose), see README for details\n" "--quiet Disable output to stdout. Use for daemon applications\n" "--ppm 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")) { Modes.interactive_rows = atoi(argv[++j]); } else if (!strcmp(argv[j],"--interactive-ttl")) { Modes.interactive_ttl = atoi(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.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); }