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dump1090/dump1090.c
antirez ec1f34f572 Fix for --metric
2013-01-08 20:02:58 +01:00

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/* Mode1090, a Mode S messages decoder for RTLSDR devices.
*
* Copyright (C) 2012 by Salvatore Sanfilippo <antirez@gmail.com>
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <pthread.h>
#include <stdint.h>
#include <errno.h>
#include <unistd.h>
#include <math.h>
#include <sys/time.h>
#include <fcntl.h>
#include <ctype.h>
#include "rtl-sdr.h"
#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_DATA_LEN (16*16384) /* 256k */
#define MODES_AUTO_GAIN -100 /* Use automatic gain. */
#define MODES_MAX_GAIN 999999 /* Use max available gain. */
#define MODES_PREAMBLE_US 8 /* microseconds */
#define MODES_LONG_MSG_BITS 112
#define MODES_SHORT_MSG_BITS 56
#define MODES_FULL_LEN (MODES_PREAMBLE_US+MODES_LONG_MSG_BITS)
#define MODES_LONG_MSG_BYTES (112/8)
#define MODES_SHORT_MSG_BYTES (56/8)
#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_DEBUG_DEMOD 1
#define MODES_DEBUG_DEMODERR 2
#define MODES_DEBUG_BADCRC 3
#define MODES_DEBUG_GOODCRC 4
#define MODES_DEBUG_NOPREAMBLE 5
/* 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_NOTUSED(V) ((void) V)
/* Structure used to describe an aircraft in iteractive mode. */
struct aircraft {
uint32_t addr; /* ICAO address */
char hexaddr[7]; /* Printable ICAO address */
char flight[9]; /* Flight number */
int altitude; /* Altitude */
int speed; /* Velocity computed from EW and NS components. */
time_t seen; /* Time at which the last packet was received. */
long messages; /* Number of Mode S messages received. */
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. */
unsigned char *data; /* Raw IQ samples buffer */
uint16_t *magnitude; /* Magnitude vector */
uint32_t data_len; /* Buffer length. */
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;
/* 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 debug; /* Debugging mode */
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. */
/* Interactive mode */
struct aircraft *aircrafts;
long long interactive_last_update; /* Last screen update in milliseconds */
/* Statistics */
long long stat_valid_preamble;
long long stat_demodulated;
long long stat_goodcrc;
long long stat_badcrc;
long long stat_fixed;
} 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. */
int aa1, aa2, aa3; /* ICAO Address bytes 1 2 and 3 */
/* DF 11 */
int ca; /* Responder capabilities. */
/* DF 17 */
int metype; /* Extended squitter message type. */
int mesub; /* Extended squitter message subtype. */
int heading_is_valid;
int heading;
int aircraft_type;
int fflag; /* Odd or Even CPR message? */
int tflag; /* UTC synchronized? */
int raw_latitude; /* Non decoded latitude */
int raw_longitude; /* Non decoded longitude */
char flight[9]; /* 8 chars flight number. */
int ew_dir; /* E/W direction. */
int ew_velocity; /* E/W velocity. */
int ns_dir; /* N/S direction. */
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 identity; /* 13 bits identity (Squawk). */
/* Fields used by multiple message types. */
int altitude, unit;
};
void interactiveShowData(void);
void interactiveReceiveData(struct modesMessage *mm);
/* ============================= Utility functions ========================== */
static long long mstime(void) {
struct timeval tv;
long long mst;
gettimeofday(&tv, NULL);
mst = ((long long)tv.tv_sec)*1000;
mst += tv.tv_usec/1000;
return mst;
}
/* =============================== Initialization =========================== */
void modesInitConfig(void) {
Modes.gain = MODES_MAX_GAIN;
Modes.dev_index = 0;
Modes.enable_agc = 0;
Modes.freq = MODES_DEFAULT_FREQ;
Modes.filename = NULL;
Modes.fix_errors = 1;
Modes.check_crc = 1;
Modes.raw = 0;
Modes.onlyaddr = 0;
Modes.debug = 0;
Modes.interactive = 0;
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);
Modes.data_len = MODES_DATA_LEN;
Modes.data_ready = 0;
/* Allocate the ICAO address cache. We use two uint32_t for every
* entry because it's a addr / timestamp pair for every entry. */
Modes.icao_cache = malloc(sizeof(uint32_t)*MODES_ICAO_CACHE_LEN*2);
memset(Modes.icao_cache,0,sizeof(Modes.icao_cache));
Modes.aircrafts = NULL;
Modes.interactive_last_update = 0;
if ((Modes.data = malloc(Modes.data_len)) == NULL ||
(Modes.magnitude = malloc(Modes.data_len*2)) == NULL) {
fprintf(stderr, "Out of memory allocating data buffer.\n");
exit(1);
}
/* Populate the I/Q -> Magnitude lookup table. It is used because
* sqrt or round may be expensive and may vary a lot depending on
* the libc used.
*
* We scale to 0-255 range multiplying by 1.4 in order to ensure that
* every different I/Q pair will result in a different magnitude value,
* not losing any resolution. */
Modes.maglut = malloc(129*129*2);
for (i = 0; i <= 128; i++) {
for (q = 0; q <= 128; q++) {
Modes.maglut[i*129+q] = round(sqrt(i*i+q*q)*360);
}
}
/* Statistics */
Modes.stat_valid_preamble = 0;
Modes.stat_demodulated = 0;
Modes.stat_goodcrc = 0;
Modes.stat_badcrc = 0;
Modes.stat_fixed = 0;
Modes.exit = 0;
}
/* =============================== RTLSDR handling ========================== */
void modesInitRTLSDR(void) {
int j;
int device_count;
int ppm_error = 0;
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, 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);
if (len > Modes.data_len) len = Modes.data_len;
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(5000);
pthread_mutex_lock(&Modes.data_mutex);
}
toread = Modes.data_len;
p = 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.data_len);
} 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 5 samples before the actual start. */
uint32_t start = (offset < padding) ? 0 : offset-padding;
uint32_t end = offset + (MODES_PREAMBLE_US*2)+(MODES_SHORT_MSG_BITS*2) - 1;
uint32_t j;
for (j = start; j <= end; j++) {
dumpMagnitudeBar(j-offset, m[j]);
}
}
/* 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
*/
void dumpRawMessage(char *descr, unsigned char *msg,
uint16_t *m, uint32_t offset)
{
int j;
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("\n");
dumpMagnitudeVector(m,offset);
printf("---\n\n");
}
/* ===================== 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;
int offset = (bits == 112) ? 0 : (112-56);
int j;
for(j = 0; j < bits; j++) {
int byte = j/8;
int bit = j%8;
int bitmask = 1 << (7-bit);
/* If bit is set, xor with corresponding table entry. */
if (msg[byte] & bitmask)
crc ^= modes_checksum_table[j+offset];
}
return crc; /* 24 bit checksum. */
}
/* Given the Downlink Format (DF) of the message, return the message length
* in bits. */
int modesMessageLenByType(int type) {
if (type == 16 || type == 17 ||
type == 19 || type == 20 ||
type == 21)
return MODES_LONG_MSG_BITS;
else
return 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_BITS/8];
for (j = 0; j < bits; j++) {
int byte = j/8;
int bitmask = 1 << (7-(j%8));
uint32_t crc1, crc2;
memcpy(aux,msg,bits/8);
aux[byte] ^= bitmask; /* Flip j-th bit. */
crc1 = ((uint32_t)aux[(bits/8)-3] << 16) |
((uint32_t)aux[(bits/8)-2] << 8) |
(uint32_t)aux[(bits/8)-1];
crc2 = modesChecksum(aux,bits);
if (crc1 == crc2) {
/* The error is fixed. Overwrite the original buffer with
* the corrected sequence, and returns the error bit
* position. */
memcpy(msg,aux,bits/8);
return j;
}
}
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;
}
/* If the message type has the checksum xored with the ICAO address, try to
* brute force it using a list of recently seen ICAO addresses.
*
* Do this in a brute-force fashion by xoring the predicted CRC with
* the address XOR checksum field in the message. This will recover the
* address: if we found it in our cache, we can assume the message is ok.
*
* On success the input buffer is modified to remove the xored checksum
* from the packet, so that the last three bytes will contain the
* plain ICAO address.
*
* If the function successfully recovers a message with a correct checksum
* it returns 1. Otherwise 0 is returned. */
int bruteForceAP(unsigned char *msg, int msgbits) {
unsigned char aux[MODES_LONG_MSG_BITS/8];
int msgtype = msg[0]>>3;
if (msgtype == 0 || /* Short air surveillance */
msgtype == 4 || /* Surveillance, altitude reply */
msgtype == 5 || /* Surveillance, identity reply */
msgtype == 16 || /* Long Air-Air survillance */
msgtype == 20 || /* Comm-A, altitude request */
msgtype == 21 || /* Comm-A, identity request */
msgtype == 24) /* Comm-C ELM */
{
uint32_t addr;
uint32_t crc;
int lastbyte = (msgbits/8)-1;
/* Work on a copy. */
memcpy(aux,msg,msgbits/8);
/* Compute the CRC of the message and XOR it with the AP field
* so that we recover the address, because:
*
* (ADDR xor CRC) xor CRC = ADDR. */
crc = modesChecksum(aux,msgbits);
aux[lastbyte] ^= crc & 0xff;
aux[lastbyte-1] ^= (crc >> 8) & 0xff;
aux[lastbyte-2] ^= (crc >> 16) & 0xff;
/* If the obtained address exists in our cache we consider
* the message valid. */
addr = aux[lastbyte] | (aux[lastbyte-1] << 8) | (aux[lastbyte-2] << 16);
if (ICAOAddressWasRecentlySeen(addr)) {
msg[lastbyte] = aux[lastbyte];
msg[lastbyte-1] = aux[lastbyte-1];
msg[lastbyte-2] = aux[lastbyte-2];
return 1;
}
}
return 0;
}
/* 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(unsigned char *msg, int *unit) {
int m_bit = msg[3] & (1<<6);
int q_bit = msg[3] & (1<<4);
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 = ((msg[2]&31)<<6) |
((msg[3]&0x80)>>2) |
((msg[3]&0x20)>>1) |
(msg[3]&15);
/* The final altitude is due to the resulting number multiplied
* by 25, minus 1000. */
return n*25-1000;
} else {
/* TODO: Implement altitude where Q=0 and M=0 */
}
} 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).
* Returns the altitude or 0 if it can't be decoded. */
int decodeAC12Field(unsigned char *msg, int *unit) {
int q_bit = msg[5] & 1;
if (q_bit) {
/* N is the 11 bit integer resulting from the removal of bit
* Q */
*unit = MODES_UNIT_FEET;
int n = ((msg[5]>>1)<<4) | ((msg[6]&0xF0) >> 4);
/* The final altitude is due to the resulting number multiplied
* by 25, minus 1000. */
return n*25-1000;
} else {
return 0;
}
}
/* 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"
};
/* ME message type to description table. */
char *me_str[] = {
};
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) {
uint32_t crc2; /* Computed CRC, used to verify the message CRC. */
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);
/* CRC is always the last three bytes. */
mm->crc = ((uint32_t)msg[(mm->msgbits/8)-3] << 16) |
((uint32_t)msg[(mm->msgbits/8)-2] << 8) |
(uint32_t)msg[(mm->msgbits/8)-1];
crc2 = modesChecksum(msg,mm->msgbits);
/* Check CRC and fix single bit errors using the CRC when
* possible (DF 11 and 17). */
mm->errorbit = -1; /* No error */
mm->crcok = (mm->crc == crc2);
if (!mm->crcok && Modes.fix_errors &&
(mm->msgtype == 11 || mm->msgtype == 17))
{
if ((mm->errorbit = fixSingleBitErrors(msg,mm->msgbits)) != -1) {
mm->crc = modesChecksum(msg,mm->msgbits);
mm->crcok = 1;
}
}
/* Note that most of the other computation happens *after* we fix
* the single bit errors, otherwise we would need to recompute the
* fields again. */
mm->ca = msg[0] & 7; /* Responder capabilities. */
/* ICAO address */
mm->aa1 = msg[1];
mm->aa2 = msg[2];
mm->aa3 = msg[3];
/* DF 17 type (assuming this is a DF17, otherwise not used) */
mm->metype = msg[4] >> 3; /* Extended squitter message type. */
mm->mesub = msg[4] & 7; /* Extended squitter message subtype. */
/* Fields for DF4,5,20,21 */
mm->fs = msg[0] & 7; /* Flight status for DF4,5,20,21 */
mm->dr = msg[1] >> 3 & 31; /* Request extraction of downlink request. */
mm->um = ((msg[1] & 7)<<3)| /* Request extraction of downlink request. */
msg[2]>>5;
mm->identity = (msg[2]&31 << 8) | msg[3]; /* 13 bits identity. */
/* Check if we can check the checksum for the Downlink Formats where
* the checksum is xored with the aircraft ICAO address. We try to
* brute force it using a list of recently seen aircraft addresses. */
if (mm->msgtype != 11 && mm->msgtype != 17) {
/* Return to the caller now if we can't resolve the API field and
* we need to check the checksum. */
if (bruteForceAP(msg,mm->msgbits)) {
/* We recovered the message!
* Populate the AA fields with the right information. */
mm->aa3 = msg[mm->msgbits/8-1];
mm->aa2 = msg[mm->msgbits/8-2];
mm->aa1 = msg[mm->msgbits/8-3];
mm->crcok = 1;
} else {
mm->crcok = 0;
}
}
/* If this is DF 11 or DF 17 and the checksum was ok,
* we can add this address to the list of recently seen
* addresses. */
if (mm->crcok && mm->errorbit == -1) {
uint32_t addr = (mm->aa1 << 16) | (mm->aa2 << 8) | mm->aa3;
addRecentlySeenICAOAddr(addr);
}
/* Decode 13 bit altitude for DF0, DF4, DF16, DF20 */
if (mm->msgtype == 0 || mm->msgtype == 4 ||
mm->msgtype == 16 || mm->msgtype == 20) {
mm->altitude = decodeAC13Field(msg, &mm->unit);
}
/* Decode extended squitter specific stuff. */
if (mm->msgtype == 17) {
/* Decode the extended squitter message. */
if (mm->metype >= 1 && mm->metype <= 4) {
/* Aircraft Identification and Category */
mm->aircraft_type = mm->metype-1;
mm->flight[0] = ais_charset[msg[5]>>2];
mm->flight[1] = ais_charset[((msg[5]&3)<<4)|(msg[6]>>4)];
mm->flight[2] = ais_charset[((msg[6]&15)<<2)|(msg[7]>>6)];
mm->flight[3] = ais_charset[msg[7]&63];
mm->flight[4] = ais_charset[msg[8]>>2];
mm->flight[5] = ais_charset[((msg[8]&3)<<4)|(msg[9]>>4)];
mm->flight[6] = ais_charset[((msg[9]&15)<<2)|(msg[10]>>6)];
mm->flight[7] = ais_charset[msg[10]&63];
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,&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 && mm->mesub >= 1 && mm->mesub <= 4) {
/* 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) >> 5;
mm->vert_rate = ((msg[8]&7) << 6) | ((msg[9]&0xfc) >> 2);
mm->velocity = sqrt(mm->ns_velocity*mm->ns_velocity+
mm->ew_velocity*mm->ew_velocity);
} else if (mm->mesub == 3 || mm->mesub == 4) {
mm->heading_is_valid = msg[5] & (1<<2);
mm->heading = (360.0/128) * (((msg[5] & 3) << 5) |
(msg[6] >> 3));
}
}
}
}
/* 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;
/* Handle only addresses mode first. */
if (Modes.onlyaddr) {
printf("%02x%02x%02x\n", mm->aa1, mm->aa2, mm->aa3);
return;
}
/* Show the raw message. */
printf("*");
for (j = 0; j < mm->msgbits/8; j++) printf("%02x", mm->msg[j]);
printf(";\n");
if (Modes.raw) return; /* Enough for --raw mode */
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 : %02x%02x%02x\n", mm->aa1, mm->aa2, mm->aa3);
} 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 : %02x%02x%02x\n", mm->aa1, mm->aa2, mm->aa3);
if (mm->msgtype == 20) {
/* TODO: 56 bits DF20 MB additional field. */
}
} 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 : %o (octal)\n", mm->identity);
printf(" ICAO Address : %02x%02x%02x\n", mm->aa1, mm->aa2, mm->aa3);
if (mm->msgtype == 21) {
/* TODO: 56 bits DF21 MB additional field. */
}
} 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: %02x%02x%02x\n", mm->aa1, mm->aa2, mm->aa3);
} 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 : %02x%02x%02x\n", mm->aa1, mm->aa2, mm->aa3);
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. */
char *ac_type_str[4] = {
"Aircraft Type D",
"Aircraft Type C",
"Aircraft Type B",
"Aircraft Type A"
};
printf(" Aircraft Type : %s\n", ac_type_str[mm->aircraft_type]);
printf(" Identification : %s\n", mm->flight);
} else if (mm->metype >= 9 && mm->metype <= 18) {
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 && mm->mesub >= 1 && mm->mesub <= 4) {
if (mm->mesub == 1 || mm->mesub == 2) {
/* Velocity */
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 type: %d subtype: %d\n",
mm->metype, mm->mesub);
}
} else {
if (Modes.check_crc)
printf("DF %d with good CRC received "
"(decoding still not implemented).\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;
unsigned char *p = Modes.data;
uint32_t j;
/* 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.data_len; j += 2) {
int i = p[j]-127;
int q = p[j+1]-127;
if (i < 0) i = -i;
if (q < 0) q = -q;
m[j/2] = Modes.maglut[i*129+q];
}
}
/* 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 bits[MODES_LONG_MSG_BITS];
unsigned char msg[MODES_LONG_MSG_BITS/2];
uint32_t j;
/* 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 - MODES_FULL_LEN*2; j++) {
int low, high, i, errors;
/* 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 (!(m[j] > m[j+1] &&
m[j+1] < m[j+2] &&
m[j+2] > m[j+3] &&
m[j+3] < m[j] &&
m[j+4] < m[j] &&
m[j+5] < m[j] &&
m[j+6] < m[j] &&
m[j+7] > m[j+8] &&
m[j+8] < m[j+9] &&
m[j+9] > m[j+6]))
{
if (Modes.debug == MODES_DEBUG_NOPREAMBLE &&
m[j] > 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. */
high = (m[j]+m[j+2]+m[j+7]+m[j+9])/4;
if (m[j+3] >= high ||
m[j+4] >= high ||
m[j+5] >= high ||
m[j+6] >= high)
{
if (Modes.debug == MODES_DEBUG_NOPREAMBLE &&
m[j] > MODES_DEBUG_NOPREAMBLE_LEVEL)
dumpRawMessage("Too high level in samples between 3 and 6",
msg, m, j);
continue;
}
/* Similarly samples in the range 10-15 must be low, as it is the
* space between the preamble and real data. */
if (m[j+10] >= high ||
m[j+11] >= high ||
m[j+12] >= high ||
m[j+13] >= high ||
m[j+14] >= high ||
m[j+15] >= high)
{
if (Modes.debug == MODES_DEBUG_NOPREAMBLE &&
m[j] > MODES_DEBUG_NOPREAMBLE_LEVEL)
dumpRawMessage("Too high level in samples between 10 and 15",
msg, m, j);
continue;
}
Modes.stat_valid_preamble++;
/* Decode all the next 112 bits, regardless of the actual message
* size. We'll check the actual message type later. */
errors = 0;
for (i = 0; i < MODES_LONG_MSG_BITS*2; i += 2) {
low = m[j+i+MODES_PREAMBLE_US*2];
high = m[j+i+MODES_PREAMBLE_US*2+1];
if (low == high) {
/* Checking if two adiacent samples have the same magnitude
* is an effective way to detect if it's just random noise
* that was detected as a valid preamble. */
bits[i/2] = 2; /* error */
if (i < MODES_SHORT_MSG_BITS*2) errors++;
} else if (low > high) {
bits[i/2] = 1;
} else {
/* (low < high) for exclusion */
bits[i/2] = 0;
}
}
/* Pack bits into bytes */
for (i = 0; i < MODES_LONG_MSG_BITS; i += 8) {
msg[i/8] =
bits[i]<<7 |
bits[i+1]<<6 |
bits[i+2]<<5 |
bits[i+3]<<4 |
bits[i+4]<<3 |
bits[i+5]<<2 |
bits[i+6]<<1 |
bits[i+7];
}
int msgtype = msg[0]>>3;
int msglen = modesMessageLenByType(msgtype)/8;
/* Last check, high and low bits are different enough in magnitude
* to mark this as real message and not just noise? */
int delta = 0;
for (i = 0; i < msglen*8*2; i += 2) {
delta += abs(m[j+i+MODES_PREAMBLE_US*2]-
m[j+i+MODES_PREAMBLE_US*2+1]);
}
delta /= msglen*4;
/* Filter for an average delta of three is small enough to let almost
* every kind of message to pass, but high enough to filter some
* random noise. */
if (delta < 10*255) continue;
/* If we reached this point, and error is zero, we are very likely
* with a Mode S message in our hands, but it may still be broken
* and CRC may not be correct. This is handled by the next layer. */
if (errors == 0) {
struct modesMessage mm;
/* Decode the received message and update statistics */
decodeModesMessage(&mm,msg);
Modes.stat_demodulated++;
if (mm.errorbit == -1) {
if (mm.crcok)
Modes.stat_goodcrc++;
else
Modes.stat_badcrc++;
} else {
Modes.stat_badcrc++;
Modes.stat_fixed++;
}
/* Output debug mode info if needed. */
if (Modes.debug == MODES_DEBUG_DEMOD)
dumpRawMessage("Demodulated with 0 errors", msg, m, j);
else if (Modes.debug == MODES_DEBUG_BADCRC && !mm.crcok)
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);
/* Pass data to the next layer */
if (!Modes.stats && (Modes.check_crc == 0 || mm.crcok)) {
if (Modes.interactive) {
interactiveReceiveData(&mm);
} else {
displayModesMessage(&mm);
if (!Modes.raw && !Modes.onlyaddr) printf("\n");
}
}
/* Skip this message if we are sure it's fine. */
if (mm.crcok) j += (MODES_PREAMBLE_US+(msglen*8))*2;
} else {
if (Modes.debug == MODES_DEBUG_DEMODERR) {
printf("The following message has %d demod errors\n", errors);
dumpRawMessage("Demodulated with errors", msg, m, j);
}
}
}
}
/* ========================= Interactive mode =============================== */
/* Return a new aircraft structure for the interactive mode linked list
* of aircrafts. */
struct aircraft *interactiveCreateAircraft(uint32_t addr) {
struct aircraft *a = malloc(sizeof(*a));
a->addr = addr;
snprintf(a->hexaddr,sizeof(a->hexaddr),"%06x",(int)addr);
a->flight[0] = '\0';
a->altitude = 0;
a->speed = 0;
a->seen = time(NULL);
a->messages = 0;
a->next = NULL;
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;
}
/* Receive new messages and populate the interactive mode with more info. */
void interactiveReceiveData(struct modesMessage *mm) {
uint32_t addr;
struct aircraft *a, *aux;
if (Modes.check_crc && mm->crcok == 0) return;
addr = (mm->aa1 << 16) | (mm->aa2 << 8) | mm->aa3;
/* Loookup our aircraft or create a new one. */
a = interactiveFindAircraft(addr);
if (!a) {
a = interactiveCreateAircraft(addr);
a->next = Modes.aircrafts;
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->seen = time(NULL);
a->messages++;
if (mm->msgtype == 0 || mm->msgtype == 4 || mm->msgtype == 20) {
a->altitude = mm->altitude;
} 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) {
a->altitude = mm->altitude;
} else if (mm->metype == 19) {
if (mm->mesub == 1 || mm->mesub == 2) {
a->speed = mm->velocity;
}
}
}
}
/* Show the currently captured interactive data on screen. */
void interactiveShowData(void) {
struct aircraft *a = Modes.aircrafts;
time_t now = time(NULL);
char progress[4];
int count = 0;
memset(progress,' ',3);
progress[time(NULL)%3] = '.';
progress[3] = '\0';
printf("\x1b[H\x1b[2J"); /* Clear the screen */
printf("Hex Flight Altitude Speed Messages Seen %s\n",
progress);
printf("-------------------------------------------------------\n");
while(a && count < Modes.interactive_rows) {
int altitude = a->altitude, speed = a->speed;
/* Convert units to metric if --metric was specified. */
if (Modes.metric) {
altitude /= 3.2828;
speed *= 1.852;
}
printf("%-6s %-8s %-9d %-9d %-9ld %d sec ago\n",
a->hexaddr, a->flight, altitude, speed, a->messages,
(int)(now - a->seen));
a = a->next;
count++;
}
}
/* 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;
long long c = 0;
while ((i = getchar()) != EOF && (q = getchar()) != EOF) {
if (abs(i-127) < level && abs(q-127) < level) {
c++;
if (c > MODES_PREAMBLE_US*4) continue;
} else {
c = 0;
}
putchar(i);
putchar(q);
}
}
/* ================================ Main ==================================== */
void showHelp(void) {
printf(
"--device-index <index> Select RTL device (default: 0).\n"
"--gain <db> Set gain (default: max gain. Use -100 for auto-gain).\n"
"--enable-agc <db> Enable the Automatic Gain Control (default: off).\n"
"--freq <hz> Set frequency (default: 1090 Mhz).\n"
"--ifile <filename> Read data from file (use '-' for stdin).\n"
"--interactive Interactive mode refreshing data on screen.\n"
"--interactive-rows <num> Max number of rows in interactive mode (default: 15).\n"
"--interactive-ttl <sec> Remove from list if idle for <sec> (default: 60).\n"
"--raw Show only messages hex values.\n"
"--no-fix Disable single-bits error correction using CRC.\n"
"--no-crc-check Disable messages with broken CRC (discouraged).\n"
"--stats With --ifile print stats at exit. No other output.\n"
"--onlyaddr Show only ICAO addresses (testing purposes).\n"
"--metric Use metric units (meters, km/h, ...).\n"
"--snip <level> Strip IQ file removing samples < level.\n"
"--debug <level> Debug mode, see README for more information.\n"
"--help Show this help.\n"
);
}
int main(int argc, char **argv) {
int j;
/* Set sane defaults. */
modesInitConfig();
/* 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 = 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 = strtoll(argv[++j],NULL,10);
} else if (!strcmp(argv[j],"--ifile") && more) {
Modes.filename = strdup(argv[++j]);
} else if (!strcmp(argv[j],"--no-fix")) {
Modes.fix_errors = 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],"--onlyaddr")) {
Modes.onlyaddr = 1;
} else if (!strcmp(argv[j],"--metric")) {
Modes.metric = 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) {
Modes.debug = atoi(argv[++j]);
} 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 {
fprintf(stderr,
"Unknown or not enough arguments for option '%s'.\n\n",
argv[j]);
showHelp();
exit(1);
}
}
modesInit();
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);
}
}
/* 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();
/* 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.data_len/2);
/* Refresh screen when in interactive mode. */
if (Modes.interactive &&
(mstime() - Modes.interactive_last_update) >
MODES_INTERACTIVE_REFRESH_TIME)
{
interactiveRemoveStaleAircrafts();
interactiveShowData();
Modes.interactive_last_update = mstime();
}
pthread_mutex_lock(&Modes.data_mutex);
if (Modes.exit) break;
}
/* If --ifile and --stats were given, print statistics. */
if (Modes.stats && Modes.filename) {
printf("%lld valid preambles\n", Modes.stat_valid_preamble);
printf("%lld demodulated with zero errors\n", Modes.stat_demodulated);
printf("%lld with good crc\n", Modes.stat_goodcrc);
printf("%lld with bad crc\n", Modes.stat_badcrc);
printf("%lld single bit errors corrected\n", Modes.stat_fixed);
}
rtlsdr_close(Modes.dev);
return 0;
}
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