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-rw-r--r--utils/rtl_adsb.c496
1 files changed, 496 insertions, 0 deletions
diff --git a/utils/rtl_adsb.c b/utils/rtl_adsb.c
new file mode 100644
index 0000000..7de9204
--- /dev/null
+++ b/utils/rtl_adsb.c
@@ -0,0 +1,496 @@
+/*
+ * 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"
+ "\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;
+}
+
+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;
+}
+
+inline uint16_t min16(uint16_t a, uint16_t b)
+{
+ return a<b ? a : b;
+}
+
+inline uint16_t max16(uint16_t a, uint16_t b)
+{
+ return a>b ? a : b;
+}
+
+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;
+ pthread_cond_init(&ready, NULL);
+ pthread_mutex_init(&ready_m, NULL);
+ squares_precompute();
+
+ while ((opt = getopt(argc, argv, "d:g:p:e:Q:VS")) != -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;
+ 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);
+
+ /* 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_cond_destroy(&ready);
+ pthread_mutex_destroy(&ready_m);
+
+ if (file != stdout) {
+ fclose(file);}
+
+ rtlsdr_close(dev);
+ free(buffer);
+ return r >= 0 ? r : -r;
+}
+
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