Osmcoom ADS-B test signal generator https://osmocom.org/projects/sdr
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osmo-adsb-gen/adsb_gen.c

216 lines
4.7 KiB

/* (C) 2014 by Harald Welte <laforge@gnumonks.org>
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation; either version 3 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <osmocom/core/bits.h>
#include <osmocom/core/utils.h>
#define PREAMBLE_LEN 8
#define SHORT_LEN 56
#define LONG_LEN 112
#define OUTBUF_SIZE ((LONG_LEN+PREAMBLE_LEN)*2)
#define SPACE 0xff
static const ubit_t preamble[PREAMBLE_LEN] = { 1, 1, SPACE, 0, 0, SPACE, SPACE, SPACE };
/* encode Pulse Position Modulation */
static int ppm_encode(ubit_t *out, const ubit_t *in, unsigned int num_in)
{
int i;
int j = 0;
for (i = 0; i < num_in; i++) {
switch (in[i]) {
case 0:
out[j++] = 0;
out[j++] = 1;
break;
case 1:
out[j++] = 1;
out[j++] = 0;
break;
case SPACE:
out[j++] = 0;
out[j++] = 0;
break;
default:
return -1;
}
}
return 0;
}
int modes_encode_from_bin(ubit_t *out, const pbit_t *bin, unsigned int num_bits)
{
ubit_t bitbuf[PREAMBLE_LEN+LONG_LEN];
int rc, out_len;
printf("from_bin(num_bits=%u)\n", num_bits);
/* assemble the un-encoded bits of the entire message */
memcpy(bitbuf, preamble, sizeof(preamble));
rc = osmo_pbit2ubit(bitbuf+sizeof(preamble), bin, num_bits);
printf("sym=%s\n", osmo_ubit_dump(bitbuf, num_bits+sizeof(preamble)));
/* encode using pulse-position modulation */
rc = ppm_encode(out, bitbuf, num_bits+sizeof(preamble));
if (rc < 0) {
fprintf(stderr, "Error during ppm_encode\n");
return rc;
}
out_len = 2*(num_bits + sizeof(preamble));
printf("out=%s\n", osmo_ubit_dump(out, out_len));
return out_len;
}
int modes_encode_from_ascii(ubit_t *out, const char *in)
{
char ascbuf[LONG_LEN*2];
ubit_t binbuf[LONG_LEN];
int str_len = strlen(in);
int num_bytes = (str_len - 2) / 2;
int rc;
/* sanity checking */
if (str_len > LONG_LEN*2 + 2) {
fprintf(stderr, "String too long!\n");
return -1;
}
if (in[0] != '*' || in[strlen(in)-1] != ';') {
fprintf(stderr, "string `%s' not in correct format\n", in);
return -2;
}
/* copy string, skipping heading '*' and trailing ';' */
memset(ascbuf, 0, sizeof(ascbuf));
strncpy(ascbuf, in+1, str_len-2);
/* convert from hex to binary */
rc = osmo_hexparse(ascbuf, binbuf, sizeof(binbuf));
if (rc < 0) {
fprintf(stderr, "error during hexparse of `%s'\n", ascbuf);
return rc;
}
/* encode the actual binary */
return modes_encode_from_bin(out, binbuf, num_bytes*8);
}
static int outfd;
/* write a frame to the output file */
static int put_frame(const ubit_t *frame, unsigned int num_bits)
{
return write(outfd, frame, num_bits);
}
/* write a pause to the output file (given duration in usec) */
static int put_pause(unsigned int usec)
{
uint8_t buf[100000];
unsigned int i, num_samples = usec * 2;
unsigned int written = 0;
memset(buf, 0, sizeof(buf));
for (i = 0; i < num_samples; i += written) {
unsigned int pending = num_samples - i;
int rc;
written = pending;
if (written > sizeof(buf))
written = sizeof(buf);
rc = write(outfd, buf, written);
if (rc < written)
return -1;
}
return 0;
}
int main(int argc, char **argv)
{
int rc;
char line[255];
uint8_t outbuf[OUTBUF_SIZE];
char *infname, *outfname;
FILE *infile;
int opt, pause_usec = 1000000;
while ((opt = getopt(argc, argv, "p:")) != -1) {
switch (opt) {
case 'p':
pause_usec = atoi(optarg);
break;
default:
exit(2);
}
}
if (argc <= optind+1) {
fprintf(stderr, "Usage: %s [-p pause_usec] <infname> <outfname>\n", argv[0]);
exit(2);
}
infname = argv[optind];
outfname = argv[optind+1];
infile = fopen(infname, "r");
if (!infile)
exit(2);
outfd = open(outfname, O_CREAT|O_WRONLY|O_TRUNC, 0660);
if (outfd < 0)
exit(2);
while (fgets(line, sizeof(line), infile)) {
if (!strlen(line))
continue;
if (line[strlen(line)-1] == '\n')
line[strlen(line)-1] = '\0';
printf("IN: %s\n", line);
rc = modes_encode_from_ascii(outbuf, line);
if (rc < 0)
exit(-rc);
put_frame(outbuf, rc);
put_pause(pause_usec);
}
fclose(infile);
close(outfd);
exit(0);
}