/* decode GLONASS navigation data ----------------------------------------------
* decode GLONASS navigation data and extract ephemeris
* args : sdrnav_t *nav I/O sdr navigation struct
* return : int string number (1-5)
*-----------------------------------------------------------------------------*/
extern int decode_g1(sdrnav_t *nav)
{
int i,id=0,bits1[170],bits2[85];
uint8_t bin[11]; /* 85/8 word bits */
/* remove meandr from data */
for (i=0;i<170;i++) {
if (i%2==0)
bits1[i]= nav->polarity*nav->fbits[i];
else
bits1[i]=-nav->polarity*nav->fbits[i];
}
for (i=0;i<84;i++) {
bits2[i+1]=bits1[2*i]*bits1[2*(i+1)];
}
bits2[0] = -1;
bits2byte(bits2,85,11,0,bin);
/* decode navigation data */
id=decode_flame_g1(bin,&nav->sdreph);
if (id<1||id>15)
SDRPRINTF("error: GLONASS word number sfn=%d\n",id);
return id;
}
void print_frame(int len) {
int i;
int byte;
//int err = 0;
printf("\n");
for (i = 0; i < len; i++) {
byte = bits2byte(bitframe+10*i+2);
frame[i] = byte;
//printf("%02X ", byte);
}
if (option_raw) {
for (i = 0; i < len; i++) {
fprintf(stdout, "%02x ", frame[i]);
}
fprintf(stdout, "\n");
}
//else
{
if ((frame[0] == 0x01) && (frame[1] == 0x02)) { // GPS Data Packet
print_gps(0x00); // packet offset in frame
fprintf(stdout, "\n");
}
}
}
/* check Galileo E1B CRC -------------------------------------------------------
* compute and check CRC of Galileo E1B page data
* args : uint8_t *data1 I E1B page part 1 (15 bytes (120 bits))
* uint8_t *data2 I E1B page part 2 (15 bytes (120 bits))
* return : int 1:okay 0: wrong parity
*-----------------------------------------------------------------------------*/
extern int checkcrc_e1b(uint8_t *data1, uint8_t *data2)
{
uint8_t crcbins[25]={0};
int i,j,crcbits[196],crc,crcmsg;
/* page part 1 */
for (i=0;i<15;i++) {
for (j=0;j<8;j++) {
if (8*i+j==114) break;
crcbits[8*i+j]=-2*(((data1[i]<<j)&0x80)>>7)+1;
}
}
/* page part 2 */
for (i=0;i<11;i++) {
for (j=0;j<8;j++) {
if (8*i+j==82) break;
crcbits[114+8*i+j]=-2*(((data2[i]<<j)&0x80)>>7)+1;
}
}
bits2byte(crcbits,196,25,1,crcbins); /* right alignment for crc */
crc=crc24q(crcbins,25); /* compute crc24 */
crcmsg=getbitu(data2,82,24); /* crc in message */
/* crc matching */
if (crc==crcmsg) return 0;
else return -1;
}
/* decode GPS/QZS L1CA navigation data -----------------------------------------
* decode GPS/QZS L1CA navigation data and extract ephemeris
* args : sdrnav_t *nav I/O sdr navigation struct
* return : int subframe ID (1-5)
*-----------------------------------------------------------------------------*/
extern int decode_l1ca(sdrnav_t *nav)
{
int i,j,id=0;
uint8_t bin[38];
/* bit inversion */
for (i=0;i<10;i++) {
if (nav->fbitsdec[i*30+1]==-1) {
for (j=2;j<26;j++)
nav->fbitsdec[i*30+j]*=-1;
}
}
bits2byte(&nav->fbitsdec[nav->addflen],nav->flen,38,0,bin);
/* decode navigation data */
id=decode_frame_l1ca(bin,&nav->sdreph);
if (id<1||id>5)
SDRPRINTF("error: GPS subframe number sfn=%d\n",id);
return id;
}
int main(int argc, char *argv[]) {
FILE *fp;
char bitbuf[8];
int bit_count = 0,
byte_count = FRAMESTART,
header_found = 0,
byte, i;
int bit, len;
++argv;
while ((*argv) && (!wavloaded)) {
if ( (strcmp(*argv, "-v") == 0) || (strcmp(*argv, "--verbose") == 0) ) {
option_verbose = 1;
}
else if ( (strcmp(*argv, "-r") == 0) || (strcmp(*argv, "--raw") == 0) ) {
option_raw = 1;
}
else {
if ( !(fp = fopen(*argv, "rb")) ) {
fprintf(stderr, "%s konnte nicht geoeffnet werden\n", *argv);
return -1;
}
else wavloaded = 1;
}
++argv;
}
if (!wavloaded) {
fprintf(stderr, "rs41sg [options] <rs41_audio.wav>\n");
fprintf(stderr, " options:\n");
fprintf(stderr, " -v, --verbose\n");
fprintf(stderr, " -r, --raw\n");
return -1;
}
i = read_wav_header(fp);
if (i) {
fclose(fp);
return -1;
}
while (!read_bits_fsk(fp, &bit, &len)) {
if (len == 0) { // reset_frame();
if (byte_count > FRAME_LEN-20) print_frame(byte_count);
bit_count = 0;
byte_count = FRAMESTART;
header_found = 0;
inc_bufpos();
buf[bufpos] = 'x';
continue; // ...
}
for (i = 0; i < len; i++) {
inc_bufpos();
buf[bufpos] = 0x30 + bit; // Ascii
if (!header_found) {
if (compare() >= HEADLEN) header_found = 1;
}
else {
bitbuf[bit_count] = bit;
bit_count++;
if (bit_count == 8) {
bit_count = 0;
byte = bits2byte(bitbuf);
frame[byte_count] = byte;
byte_count++;
if (byte_count == FRAME_LEN) {
byte_count = FRAMESTART;
header_found = 0;
print_frame(FRAME_LEN);
}
}
}
}
}
fclose(fp);
return 0;
}