Software to turn the RTL2832U into a SDR receiver
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rtl-sdr/src/rtl_adsb.c

507 lines
12 KiB

/*
* rtl-sdr, turns your Realtek RTL2832 based DVB dongle into a SDR receiver
* Copyright (C) 2012 by Steve Markgraf <steve@steve-m.de>
* Copyright (C) 2012 by Hoernchen <la@tfc-server.de>
* Copyright (C) 2012 by Kyle Keen <keenerd@gmail.com>
* Copyright (C) 2012 by Youssef Touil <youssef@sdrsharp.com>
* Copyright (C) 2012 by Ian Gilmour <ian@sdrsharp.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#ifndef _WIN32
#include <unistd.h>
#else
#include <windows.h>
#include <fcntl.h>
#include <io.h>
#include "getopt/getopt.h"
#endif
#include <pthread.h>
#include <libusb.h>
#include "rtl-sdr.h"
#include "convenience/convenience.h"
#ifdef _WIN32
#define sleep Sleep
#if defined(_MSC_VER) && (_MSC_VER < 1800)
#define round(x) (x > 0.0 ? floor(x + 0.5): ceil(x - 0.5))
#endif
#endif
#define ADSB_RATE 2000000
#define ADSB_FREQ 1090000000
#define DEFAULT_ASYNC_BUF_NUMBER 12
#define DEFAULT_BUF_LENGTH (16 * 16384)
#define AUTO_GAIN -100
#define MESSAGEGO 253
#define OVERWRITE 254
#define BADSAMPLE 255
static pthread_t demod_thread;
static pthread_cond_t ready;
static pthread_mutex_t ready_m;
static volatile int do_exit = 0;
static rtlsdr_dev_t *dev = NULL;
uint16_t squares[256];
/* todo, bundle these up in a struct */
uint8_t *buffer; /* also abused for uint16_t */
int verbose_output = 0;
int short_output = 0;
int quality = 10;
int allowed_errors = 5;
FILE *file;
int adsb_frame[14];
#define preamble_len 16
#define long_frame 112
#define short_frame 56
/* signals are not threadsafe by default */
#define safe_cond_signal(n, m) pthread_mutex_lock(m); pthread_cond_signal(n); pthread_mutex_unlock(m)
#define safe_cond_wait(n, m) pthread_mutex_lock(m); pthread_cond_wait(n, m); pthread_mutex_unlock(m)
void usage(void)
{
fprintf(stderr,
"rtl_adsb, a simple ADS-B decoder\n\n"
"Use:\trtl_adsb [-R] [-g gain] [-p ppm] [output file]\n"
"\t[-d device_index (default: 0)]\n"
"\t[-V verbove output (default: off)]\n"
"\t[-S show short frames (default: off)]\n"
"\t[-Q quality (0: no sanity checks, 0.5: half bit, 1: one bit (default), 2: two bits)]\n"
"\t[-e allowed_errors (default: 5)]\n"
"\t[-g tuner_gain (default: automatic)]\n"
"\t[-p ppm_error (default: 0)]\n"
"\t[-T enable bias-T on GPIO PIN 0 (works for rtl-sdr.com v3 dongles)]\n"
"\tfilename (a '-' dumps samples to stdout)\n"
"\t (omitting the filename also uses stdout)\n\n"
"Streaming with netcat:\n"
"\trtl_adsb | netcat -lp 8080\n"
"\twhile true; do rtl_adsb | nc -lp 8080; done\n"
"Streaming with socat:\n"
"\trtl_adsb | socat -u - TCP4:sdrsharp.com:47806\n"
"\n");
exit(1);
}
#ifdef _WIN32
BOOL WINAPI
sighandler(int signum)
{
if (CTRL_C_EVENT == signum) {
fprintf(stderr, "Signal caught, exiting!\n");
do_exit = 1;
rtlsdr_cancel_async(dev);
return TRUE;
}
return FALSE;
}
#else
static void sighandler(int signum)
{
fprintf(stderr, "Signal caught, exiting!\n");
do_exit = 1;
rtlsdr_cancel_async(dev);
}
#endif
void display(int *frame, int len)
{
int i, df;
if (!short_output && len <= short_frame) {
return;}
df = (frame[0] >> 3) & 0x1f;
if (quality == 0 && !(df==11 || df==17 || df==18 || df==19)) {
return;}
fprintf(file, "*");
for (i=0; i<((len+7)/8); i++) {
fprintf(file, "%02x", frame[i]);}
fprintf(file, ";\r\n");
if (!verbose_output) {
return;}
fprintf(file, "DF=%i CA=%i\n", df, frame[0] & 0x07);
fprintf(file, "ICAO Address=%06x\n", frame[1] << 16 | frame[2] << 8 | frame[3]);
if (len <= short_frame) {
return;}
fprintf(file, "PI=0x%06x\n", frame[11] << 16 | frame[12] << 8 | frame[13]);
fprintf(file, "Type Code=%i S.Type/Ant.=%x\n", (frame[4] >> 3) & 0x1f, frame[4] & 0x07);
fprintf(file, "--------------\n");
}
int abs8(int x)
/* do not subtract 127 from the raw iq, this handles it */
{
if (x >= 127) {
return x - 127;}
return 127 - x;
}
void squares_precompute(void)
/* equiv to abs(x-128) ^ 2 */
{
int i, j;
// todo, check if this LUT is actually any faster
for (i=0; i<256; i++) {
j = abs8(i);
squares[i] = (uint16_t)(j*j);
}
}
int magnitute(uint8_t *buf, int len)
/* takes i/q, changes buf in place (16 bit), returns new len (16 bit) */
{
int i;
uint16_t *m;
for (i=0; i<len; i+=2) {
m = (uint16_t*)(&buf[i]);
*m = squares[buf[i]] + squares[buf[i+1]];
}
return len/2;
}
static inline uint16_t single_manchester(uint16_t a, uint16_t b, uint16_t c, uint16_t d)
/* takes 4 consecutive real samples, return 0 or 1, BADSAMPLE on error */
{
int bit, bit_p;
bit_p = a > b;
bit = c > d;
if (quality == 0) {
return bit;}
if (quality == 5) {
if ( bit && bit_p && b > c) {
return BADSAMPLE;}
if (!bit && !bit_p && b < c) {
return BADSAMPLE;}
return bit;
}
if (quality == 10) {
if ( bit && bit_p && c > b) {
return 1;}
if ( bit && !bit_p && d < b) {
return 1;}
if (!bit && bit_p && d > b) {
return 0;}
if (!bit && !bit_p && c < b) {
return 0;}
return BADSAMPLE;
}
if ( bit && bit_p && c > b && d < a) {
return 1;}
if ( bit && !bit_p && c > a && d < b) {
return 1;}
if (!bit && bit_p && c < a && d > b) {
return 0;}
if (!bit && !bit_p && c < b && d > a) {
return 0;}
return BADSAMPLE;
}
static inline uint16_t min16(uint16_t a, uint16_t b)
{
return a<b ? a : b;
}
static inline uint16_t max16(uint16_t a, uint16_t b)
{
return a>b ? a : b;
}
static inline int preamble(uint16_t *buf, int i)
/* returns 0/1 for preamble at index i */
{
int i2;
uint16_t low = 0;
uint16_t high = 65535;
for (i2=0; i2<preamble_len; i2++) {
switch (i2) {
case 0:
case 2:
case 7:
case 9:
//high = min16(high, buf[i+i2]);
high = buf[i+i2];
break;
default:
//low = max16(low, buf[i+i2]);
low = buf[i+i2];
break;
}
if (high <= low) {
return 0;}
}
return 1;
}
void manchester(uint16_t *buf, int len)
/* overwrites magnitude buffer with valid bits (BADSAMPLE on errors) */
{
/* a and b hold old values to verify local manchester */
uint16_t a=0, b=0;
uint16_t bit;
int i, i2, start, errors;
int maximum_i = len - 1; // len-1 since we look at i and i+1
// todo, allow wrap across buffers
i = 0;
while (i < maximum_i) {
/* find preamble */
for ( ; i < (len - preamble_len); i++) {
if (!preamble(buf, i)) {
continue;}
a = buf[i];
b = buf[i+1];
for (i2=0; i2<preamble_len; i2++) {
buf[i+i2] = MESSAGEGO;}
i += preamble_len;
break;
}
i2 = start = i;
errors = 0;
/* mark bits until encoding breaks */
for ( ; i < maximum_i; i+=2, i2++) {
bit = single_manchester(a, b, buf[i], buf[i+1]);
a = buf[i];
b = buf[i+1];
if (bit == BADSAMPLE) {
errors += 1;
if (errors > allowed_errors) {
buf[i2] = BADSAMPLE;
break;
} else {
bit = a > b;
/* these don't have to match the bit */
a = 0;
b = 65535;
}
}
buf[i] = buf[i+1] = OVERWRITE;
buf[i2] = bit;
}
}
}
void messages(uint16_t *buf, int len)
{
int i, data_i, index, shift, frame_len;
// todo, allow wrap across buffers
for (i=0; i<len; i++) {
if (buf[i] > 1) {
continue;}
frame_len = long_frame;
data_i = 0;
for (index=0; index<14; index++) {
adsb_frame[index] = 0;}
for(; i<len && buf[i]<=1 && data_i<frame_len; i++, data_i++) {
if (buf[i]) {
index = data_i / 8;
shift = 7 - (data_i % 8);
adsb_frame[index] |= (uint8_t)(1<<shift);
}
if (data_i == 7) {
if (adsb_frame[0] == 0) {
break;}
if (adsb_frame[0] & 0x80) {
frame_len = long_frame;}
else {
frame_len = short_frame;}
}
}
if (data_i < (frame_len-1)) {
continue;}
display(adsb_frame, frame_len);
fflush(file);
}
}
static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
{
if (do_exit) {
return;}
memcpy(buffer, buf, len);
safe_cond_signal(&ready, &ready_m);
}
static void *demod_thread_fn(void *arg)
{
int len;
while (!do_exit) {
safe_cond_wait(&ready, &ready_m);
len = magnitute(buffer, DEFAULT_BUF_LENGTH);
manchester((uint16_t*)buffer, len);
messages((uint16_t*)buffer, len);
}
rtlsdr_cancel_async(dev);
return 0;
}
int main(int argc, char **argv)
{
#ifndef _WIN32
struct sigaction sigact;
#endif
char *filename = NULL;
int r, opt;
int gain = AUTO_GAIN; /* tenths of a dB */
int dev_index = 0;
int dev_given = 0;
int ppm_error = 0;
int enable_biastee = 0;
pthread_cond_init(&ready, NULL);
pthread_mutex_init(&ready_m, NULL);
squares_precompute();
while ((opt = getopt(argc, argv, "d:g:p:e:Q:VST")) != -1)
{
switch (opt) {
case 'd':
dev_index = verbose_device_search(optarg);
dev_given = 1;
break;
case 'g':
gain = (int)(atof(optarg) * 10);
break;
case 'p':
ppm_error = atoi(optarg);
break;
case 'V':
verbose_output = 1;
break;
case 'S':
short_output = 1;
break;
case 'e':
allowed_errors = atoi(optarg);
break;
case 'Q':
quality = (int)(atof(optarg) * 10);
break;
case 'T':
enable_biastee = 1;
break;
default:
usage();
return 0;
}
}
if (argc <= optind) {
filename = "-";
} else {
filename = argv[optind];
}
buffer = malloc(DEFAULT_BUF_LENGTH * sizeof(uint8_t));
if (!dev_given) {
dev_index = verbose_device_search("0");
}
if (dev_index < 0) {
exit(1);
}
r = rtlsdr_open(&dev, (uint32_t)dev_index);
if (r < 0) {
fprintf(stderr, "Failed to open rtlsdr device #%d.\n", dev_index);
exit(1);
}
#ifndef _WIN32
sigact.sa_handler = sighandler;
sigemptyset(&sigact.sa_mask);
sigact.sa_flags = 0;
sigaction(SIGINT, &sigact, NULL);
sigaction(SIGTERM, &sigact, NULL);
sigaction(SIGQUIT, &sigact, NULL);
sigaction(SIGPIPE, &sigact, NULL);
#else
SetConsoleCtrlHandler( (PHANDLER_ROUTINE) sighandler, TRUE );
#endif
if (strcmp(filename, "-") == 0) { /* Write samples to stdout */
file = stdout;
setvbuf(stdout, NULL, _IONBF, 0);
#ifdef _WIN32
_setmode(_fileno(file), _O_BINARY);
#endif
} else {
file = fopen(filename, "wb");
if (!file) {
fprintf(stderr, "Failed to open %s\n", filename);
exit(1);
}
}
/* Set the tuner gain */
if (gain == AUTO_GAIN) {
verbose_auto_gain(dev);
} else {
gain = nearest_gain(dev, gain);
verbose_gain_set(dev, gain);
}
verbose_ppm_set(dev, ppm_error);
r = rtlsdr_set_agc_mode(dev, 1);
/* Set the tuner frequency */
verbose_set_frequency(dev, ADSB_FREQ);
/* Set the sample rate */
verbose_set_sample_rate(dev, ADSB_RATE);
rtlsdr_set_bias_tee(dev, enable_biastee);
if (enable_biastee)
fprintf(stderr, "activated bias-T on GPIO PIN 0\n");
/* Reset endpoint before we start reading from it (mandatory) */
verbose_reset_buffer(dev);
pthread_create(&demod_thread, NULL, demod_thread_fn, (void *)(NULL));
rtlsdr_read_async(dev, rtlsdr_callback, (void *)(NULL),
DEFAULT_ASYNC_BUF_NUMBER,
DEFAULT_BUF_LENGTH);
if (do_exit) {
fprintf(stderr, "\nUser cancel, exiting...\n");}
else {
fprintf(stderr, "\nLibrary error %d, exiting...\n", r);}
rtlsdr_cancel_async(dev);
pthread_cancel(demod_thread);
pthread_join(demod_thread, NULL);
pthread_cond_destroy(&ready);
pthread_mutex_destroy(&ready_m);
if (file != stdout) {
fclose(file);}
rtlsdr_close(dev);
free(buffer);
return r >= 0 ? r : -r;
}