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authorKyle Keen <keenerd@gmail.com>2012-12-09 17:41:20 -0500
committerSteve Markgraf <steve@steve-m.de>2012-12-10 22:37:25 +0100
commit562fd7e8e3200fa876312e58427b3c9a7575d3fa (patch)
tree03a7d661a17c654e9696f5e9f2e5c22af6756226 /src/rtl_adsb.c
parentd6107bb059ad32c5787646dfe37dc87b68bc8758 (diff)
rtl_adsb: prototype
Signed-off-by: Steve Markgraf <steve@steve-m.de>
Diffstat (limited to 'src/rtl_adsb.c')
-rw-r--r--src/rtl_adsb.c463
1 files changed, 463 insertions, 0 deletions
diff --git a/src/rtl_adsb.c b/src/rtl_adsb.c
new file mode 100644
index 0000000..bdba983
--- /dev/null
+++ b/src/rtl_adsb.c
@@ -0,0 +1,463 @@
+/*
+ * 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>
+
+#ifndef _WIN32
+#include <unistd.h>
+#else
+#include <Windows.h>
+#include <fcntl.h>
+#include <io.h>
+#include "getopt/getopt.h"
+#endif
+
+#include <semaphore.h>
+#include <pthread.h>
+#include <libusb.h>
+
+#include "rtl-sdr.h"
+
+#ifdef _WIN32
+#define sleep Sleep
+#undef min
+#undef max
+#endif
+
+#define ADSB_RATE 2000000
+#define ADSB_FREQ 1090000000
+#define DEFAULT_ASYNC_BUF_NUMBER 32
+#define DEFAULT_BUF_LENGTH (128 * 16384)
+#define AUTO_GAIN -100
+
+static pthread_t demod_thread;
+static sem_t data_ready;
+static volatile int do_exit = 0;
+static rtlsdr_dev_t *dev = NULL;
+
+/* todo, bundle these up in a struct */
+uint8_t *buffer;
+int raw_output = 0;
+int short_output = 0;
+int allowed_errors = 5;
+FILE *file;
+int adsb_frame[14];
+#define preamble_len 16
+#define long_frame 112
+#define short_frame 56
+
+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[-R output raw bitstream (default: off)]\n"
+ "\t[-S show short frames (default: off)]\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 -R | netcat -lp 8080\n"
+ "\twhile true; do rtl_adsb -R | nc -lp 8080; done\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;
+ if (!short_output && len <= short_frame) {
+ return;}
+ if (raw_output) {
+ fprintf(file, "*");
+ for (i=0; i<((len+7)/8); i++) {
+ fprintf(file, "%02x", frame[i]);}
+ fprintf(file, ";\r\n");
+ return;
+ }
+ fprintf(file, "----------\n");
+ fprintf(file, "DF=%x CA=%x\n", (frame[0] >> 3) & 0x1f, 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=%x S.Type/Ant.=%x\n", (frame[4] >> 3) & 0x1f, frame[4] & 0x07);
+}
+
+int magnitute(unsigned char *buf, int len)
+/* takes i/q, changes buf in place, returns new len */
+{
+ int i, mag;
+ for (i=0; i<len; i+=2) {
+ mag = abs((int)buf[i]-128) + abs((int)buf[i+1]-128);
+ if (mag > 255) { // todo, compression
+ mag = 255;}
+ buf[i/2] = (unsigned char)mag;
+ }
+ return len/2;
+}
+
+inline unsigned char single_manchester(unsigned char a, unsigned char b, unsigned char c, unsigned char d)
+/* takes 4 consecutive real samples, return 0 or 1, 255 on error */
+{
+ int bit, bit_p;
+ bit_p = a > b;
+ bit = c > d;
+ 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 255;
+}
+
+inline unsigned char min(unsigned char a, unsigned char b)
+{
+ return a<b ? a : b;
+}
+
+inline unsigned char max(unsigned char a, unsigned char b)
+{
+ return a>b ? a : b;
+}
+
+inline int preamble(unsigned char *buf, int len, int i)
+/* returns 0/1 for preamble at index i */
+{
+ int i2;
+ unsigned char low = 0;
+ unsigned char high = 255;
+ for (i2=0; i2<preamble_len; i2++) {
+ switch (i2) {
+ case 0:
+ case 2:
+ case 7:
+ case 9:
+ high = min(high, buf[i+i2]);
+ break;
+ default:
+ low = max(low, buf[i+i2]);
+ break;
+ }
+ if (high <= low) {
+ return 0;}
+ }
+ return 1;
+}
+
+void manchester(unsigned char *buf, int len)
+/* overwrites magnitude buffer with valid bits (255 on errors) */
+{
+ /* a and b hold old values to verify local manchester */
+ unsigned char a=0, b=0;
+ unsigned char bit;
+ int i, i2, start, errors;
+ // todo, allow wrap across buffers
+ i = 0;
+ while (i < len) {
+ /* find preamble */
+ for ( ; i < (len - preamble_len); i++) {
+ if (!preamble(buf, len, i)) {
+ continue;}
+ a = buf[i];
+ b = buf[i+1];
+ for (i2=0; i2<preamble_len; i2++) {
+ buf[i+i2] = 253;}
+ i += preamble_len;
+ //printf("preamble found\n");
+ break;
+ }
+ i2 = start = i;
+ errors = 0;
+ /* mark bits until encoding breaks */
+ for ( ; i < len; i+=2, i2++) {
+ bit = single_manchester(a, b, buf[i], buf[i+1]);
+ a = buf[i];
+ b = buf[i+1];
+ if (bit == 255) {
+ errors += 1;
+ if (errors > allowed_errors) {
+ buf[i2] = 255;
+ break;
+ } else {
+ bit = 0;
+ a = 0;
+ b = 255;
+ }
+ }
+ buf[i] = buf[i+1] = 254; /* to be overwritten */
+ buf[i2] = bit;
+ }
+ // todo, nuke short segments
+ //printf("%i\n", i2 - start);
+ }
+}
+
+void messages(unsigned char *buf, int len)
+{
+ int i, i2, start, preamble_found;
+ int 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] |= (unsigned char)(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;}
+ }
+ }
+ // todo, check CRC
+ if (data_i < (frame_len-1)) {
+ continue;}
+ //fprintf(file, "bits: %i\n", data_i);
+ display(adsb_frame, frame_len);
+ fflush(file);
+ }
+}
+
+static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
+{
+ int dr_val;
+ if (do_exit) {
+ return;}
+ memcpy(buffer, buf, len);
+ sem_getvalue(&data_ready, &dr_val);
+ if (dr_val <= 0) {
+ sem_post(&data_ready);}
+}
+
+static void *demod_thread_fn(void *arg)
+{
+ int len;
+ while (!do_exit) {
+ sem_wait(&data_ready);
+ len = magnitute(buffer, DEFAULT_BUF_LENGTH);
+ manchester(buffer, len);
+ messages(buffer, len);
+ //fsync(file);
+ }
+ rtlsdr_cancel_async(dev);
+ return 0;
+}
+
+int main(int argc, char **argv)
+{
+#ifndef _WIN32
+ struct sigaction sigact;
+#endif
+ char *filename = NULL;
+ int n_read, r, opt;
+ int i, gain = AUTO_GAIN; // tenths of a dB
+ uint32_t dev_index = 0;
+ int device_count;
+ int ppm_error = 0;
+ char vendor[256], product[256], serial[256];
+ sem_init(&data_ready, 0, 0);
+
+ while ((opt = getopt(argc, argv, "g:p:e:RS")) != -1)
+ {
+ switch (opt) {
+ case 'd':
+ dev_index = atoi(optarg);
+ break;
+ case 'g':
+ gain = (int)(atof(optarg) * 10);
+ break;
+ case 'p':
+ ppm_error = atoi(optarg);
+ break;
+ case 'R':
+ raw_output = 1;
+ break;
+ case 'S':
+ short_output = 1;
+ break;
+ case 'e':
+ allowed_errors = atoi(optarg);
+ break;
+ default:
+ usage();
+ return 0;
+ }
+ }
+
+ if (argc <= optind) {
+ //usage();
+ filename = "-";
+ } else {
+ filename = argv[optind];
+ }
+
+ buffer = malloc(DEFAULT_BUF_LENGTH * sizeof(uint8_t));
+
+ device_count = rtlsdr_get_device_count();
+ if (!device_count) {
+ fprintf(stderr, "No supported devices found.\n");
+ exit(1);
+ }
+
+ fprintf(stderr, "Found %d device(s):\n", device_count);
+ for (i = 0; i < device_count; i++) {
+ rtlsdr_get_device_usb_strings(i, vendor, product, serial);
+ fprintf(stderr, " %d: %s, %s, SN: %s\n", i, vendor, product, serial);
+ }
+ fprintf(stderr, "\n");
+
+ fprintf(stderr, "Using device %d: %s\n",
+ dev_index, rtlsdr_get_device_name(dev_index));
+
+ r = rtlsdr_open(&dev, 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;
+#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) {
+ r = rtlsdr_set_tuner_gain_mode(dev, 0);
+ } else {
+ r = rtlsdr_set_tuner_gain_mode(dev, 1);
+ r = rtlsdr_set_tuner_gain(dev, gain);
+ }
+ if (r != 0) {
+ fprintf(stderr, "WARNING: Failed to set tuner gain.\n");
+ } else if (gain == AUTO_GAIN) {
+ fprintf(stderr, "Tuner gain set to automatic.\n");
+ } else {
+ fprintf(stderr, "Tuner gain set to %0.2f dB.\n", gain/10.0);
+ }
+
+ r = rtlsdr_set_freq_correction(dev, ppm_error);
+ r = rtlsdr_set_agc_mode(dev, 1);
+
+ /* Set the tuner frequency */
+ r = rtlsdr_set_center_freq(dev, ADSB_FREQ);
+ if (r < 0) {
+ fprintf(stderr, "WARNING: Failed to set center freq.\n");}
+ else {
+ fprintf(stderr, "Tuned to %u Hz.\n", ADSB_FREQ);}
+
+ /* Set the sample rate */
+ fprintf(stderr, "Sampling at %u Hz.\n", ADSB_RATE);
+ r = rtlsdr_set_sample_rate(dev, ADSB_RATE);
+ if (r < 0) {
+ fprintf(stderr, "WARNING: Failed to set sample rate.\n");}
+
+ /* Reset endpoint before we start reading from it (mandatory) */
+ r = rtlsdr_reset_buffer(dev);
+ if (r < 0) {
+ fprintf(stderr, "WARNING: Failed to reset buffers.\n");}
+
+ /* flush old junk */
+ sleep(1);
+ rtlsdr_read_sync(dev, NULL, 4096, NULL);
+
+ 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);
+
+ if (file != stdout) {
+ fclose(file);}
+
+ rtlsdr_close(dev);
+ free(buffer);
+ return r >= 0 ? r : -r;
+}
+