mirror/rtl-sdr-blog
1
0
Fork 0
mirror of https://github.com/rtlsdrblog/rtl-sdr-blog.git synced 2024-11-10 04:37:37 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity

rtl_adsb: sensitivity tweaks

Browse Source 
Signed-off-by: Steve Markgraf <steve@steve-m.de>
This commit is contained in:
Kyle Keen 2012-12-14 11:18:25 -05:00 committed by Steve Markgraf
parent 71b254a238
commit 8033414974
1 changed files with 60 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

85
src/rtl_adsb.c
View File

@ -50,8 +50,8 @@
#define ADSB_RATE 2000000 #define ADSB_RATE 2000000
#define ADSB_FREQ 1090000000 #define ADSB_FREQ 1090000000
#define DEFAULT_ASYNC_BUF_NUMBER 32 #define DEFAULT_ASYNC_BUF_NUMBER 12
#define DEFAULT_BUF_LENGTH (128 * 16384) #define DEFAULT_BUF_LENGTH (16 * 16384)
#define AUTO_GAIN -100 #define AUTO_GAIN -100
static pthread_t demod_thread; static pthread_t demod_thread;
@ -61,8 +61,9 @@ static rtlsdr_dev_t *dev = NULL;
/* todo, bundle these up in a struct */ /* todo, bundle these up in a struct */
uint8_t *buffer; uint8_t *buffer;
int raw_output = 0; int verbose_output = 0;
int short_output = 0; int short_output = 0;
double quality = 1.0;
int allowed_errors = 5; int allowed_errors = 5;
FILE *file; FILE *file;
int adsb_frame[14]; int adsb_frame[14];
@ -76,16 +77,17 @@ void usage(void)
"rtl_adsb, a simple ADS-B decoder\n\n" "rtl_adsb, a simple ADS-B decoder\n\n"
"Use:\trtl_adsb [-R] [-g gain] [-p ppm] [output file]\n" "Use:\trtl_adsb [-R] [-g gain] [-p ppm] [output file]\n"
"\t[-d device_index (default: 0)]\n" "\t[-d device_index (default: 0)]\n"
"\t[-R output raw bitstream (default: off)]\n" "\t[-V verbove output (default: off)]\n"
"\t[-S show short frames (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[-e allowed_errors (default: 5)]\n"
"\t[-g tuner_gain (default: automatic)]\n" "\t[-g tuner_gain (default: automatic)]\n"
"\t[-p ppm_error (default: 0)]\n" "\t[-p ppm_error (default: 0)]\n"
"\tfilename (a '-' dumps samples to stdout)\n" "\tfilename (a '-' dumps samples to stdout)\n"
"\t (omitting the filename also uses stdout)\n\n" "\t (omitting the filename also uses stdout)\n\n"
"Streaming with netcat:\n" "Streaming with netcat:\n"
"\trtl_adsb -R | netcat -lp 8080\n" "\trtl_adsb | netcat -lp 8080\n"
"\twhile true; do rtl_adsb -R | nc -lp 8080; done\n" "\twhile true; do rtl_adsb | nc -lp 8080; done\n"
"\n"); "\n");
exit(1); exit(1);
} }
@ -113,23 +115,25 @@ static void sighandler(int signum)
void display(int *frame, int len) void display(int *frame, int len)
{ {
int i; int i, df;
if (!short_output && len <= short_frame) { if (!short_output && len <= short_frame) {
return;} return;}
if (raw_output) { df = (frame[0] >> 3) & 0x1f;
if (quality == 0.0 && !(df==11 || df==17 || df==18 || df==19)) {
return;}
fprintf(file, "*"); fprintf(file, "*");
for (i=0; i<((len+7)/8); i++) { for (i=0; i<((len+7)/8); i++) {
fprintf(file, "%02x", frame[i]);} fprintf(file, "%02x", frame[i]);}
fprintf(file, ";\r\n"); fprintf(file, ";\r\n");
return; if (!verbose_output) {
} return;}
fprintf(file, "----------\n"); fprintf(file, "DF=%i CA=%i\n", df, frame[0] & 0x07);
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]); fprintf(file, "ICAO Address=%06x\n", frame[1] << 16 | frame[2] << 8 | frame[3]);
if (len <= short_frame) { if (len <= short_frame) {
return;} return;}
fprintf(file, "PI=0x%06x\n", frame[11] << 16 | frame[12] << 8 | frame[13]); 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); fprintf(file, "Type Code=%i S.Type/Ant.=%x\n", (frame[4] >> 3) & 0x1f, frame[4] & 0x07);
fprintf(file, "--------------\n");
} }
int magnitute(unsigned char *buf, int len) int magnitute(unsigned char *buf, int len)
@ -151,6 +155,30 @@ inline unsigned char single_manchester(unsigned char a, unsigned char b, unsigne
int bit, bit_p; int bit, bit_p;
bit_p = a > b; bit_p = a > b;
bit = c > d; bit = c > d;
if (quality == 0.0) {
return bit;}
if (quality == 0.5) {
if ( bit && bit_p && b > c) {
return 255;}
if (!bit && !bit_p && b < c) {
return 255;}
return bit;
}
if (quality == 1.0) {
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 255;
}
if ( bit && bit_p && c > b && d < a) { if ( bit && bit_p && c > b && d < a) {
return 1;} return 1;}
if ( bit && !bit_p && c > a && d < b) { if ( bit && !bit_p && c > a && d < b) {
@ -184,10 +212,12 @@ inline int preamble(unsigned char *buf, int len, int i)
case 2: case 2:
case 7: case 7:
case 9: case 9:
high = min(high, buf[i+i2]); //high = min(high, buf[i+i2]);
high = buf[i+i2];
break; break;
default: default:
low = max(low, buf[i+i2]); //low = max(low, buf[i+i2]);
low = buf[i+i2];
break; break;
} }
if (high <= low) { if (high <= low) {
@ -215,7 +245,6 @@ void manchester(unsigned char *buf, int len)
for (i2=0; i2<preamble_len; i2++) { for (i2=0; i2<preamble_len; i2++) {
buf[i+i2] = 253;} buf[i+i2] = 253;}
i += preamble_len; i += preamble_len;
//printf("preamble found\n");
break; break;
} }
i2 = start = i; i2 = start = i;
@ -231,7 +260,8 @@ void manchester(unsigned char *buf, int len)
buf[i2] = 255; buf[i2] = 255;
break; break;
} else { } else {
bit = 0; bit = a > b;
/* these don't have to match the bit */
a = 0; a = 0;
b = 255; b = 255;
} }
@ -239,8 +269,6 @@ void manchester(unsigned char *buf, int len)
buf[i] = buf[i+1] = 254; /* to be overwritten */ buf[i] = buf[i+1] = 254; /* to be overwritten */
buf[i2] = bit; buf[i2] = bit;
} }
// todo, nuke short segments
//printf("%i\n", i2 - start);
} }
} }
@ -263,18 +291,16 @@ void messages(unsigned char *buf, int len)
adsb_frame[index] |= (unsigned char)(1<<shift); adsb_frame[index] |= (unsigned char)(1<<shift);
} }
if (data_i == 7) { if (data_i == 7) {
//if (adsb_frame[0] == 0) { if (adsb_frame[0] == 0) {
// break;} break;}
if (adsb_frame[0] & 0x80) { if (adsb_frame[0] & 0x80) {
frame_len = long_frame;} frame_len = long_frame;}
else { else {
frame_len = short_frame;} frame_len = short_frame;}
} }
} }
// todo, check CRC
if (data_i < (frame_len-1)) { if (data_i < (frame_len-1)) {
continue;} continue;}
//fprintf(file, "bits: %i\n", data_i);
display(adsb_frame, frame_len); display(adsb_frame, frame_len);
fflush(file); fflush(file);
} }
@ -299,7 +325,6 @@ static void *demod_thread_fn(void *arg)
len = magnitute(buffer, DEFAULT_BUF_LENGTH); len = magnitute(buffer, DEFAULT_BUF_LENGTH);
manchester(buffer, len); manchester(buffer, len);
messages(buffer, len); messages(buffer, len);
//fsync(file);
} }
rtlsdr_cancel_async(dev); rtlsdr_cancel_async(dev);
return 0; return 0;
@ -312,14 +337,14 @@ int main(int argc, char **argv)
#endif #endif
char *filename = NULL; char *filename = NULL;
int n_read, r, opt; int n_read, r, opt;
int i, gain = AUTO_GAIN; // tenths of a dB int i, gain = AUTO_GAIN; /* tenths of a dB */
uint32_t dev_index = 0; uint32_t dev_index = 0;
int device_count; int device_count;
int ppm_error = 0; int ppm_error = 0;
char vendor[256], product[256], serial[256]; char vendor[256], product[256], serial[256];
sem_init(&data_ready, 0, 0); sem_init(&data_ready, 0, 0);
while ((opt = getopt(argc, argv, "g:p:e:RS")) != -1) while ((opt = getopt(argc, argv, "d:g:p:e:Q:VS")) != -1)
{ {
switch (opt) { switch (opt) {
case 'd': case 'd':
@ -331,8 +356,8 @@ int main(int argc, char **argv)
case 'p': case 'p':
ppm_error = atoi(optarg); ppm_error = atoi(optarg);
break; break;
case 'R': case 'V':
raw_output = 1; verbose_output = 1;
break; break;
case 'S': case 'S':
short_output = 1; short_output = 1;
@ -340,6 +365,9 @@ int main(int argc, char **argv)
case 'e': case 'e':
allowed_errors = atoi(optarg); allowed_errors = atoi(optarg);
break; break;
case 'Q':
quality = atof(optarg);
break;
default: default:
usage(); usage();
return 0; return 0;
@ -347,7 +375,6 @@ int main(int argc, char **argv)
} }
if (argc <= optind) { if (argc <= optind) {
//usage();
filename = "-"; filename = "-";
} else { } else {
filename = argv[optind]; filename = argv[optind];