static gps_mask_t decode_itk_subframe(struct gps_device_t *session,
unsigned char *buf, size_t len)
{
unsigned short flags, prn, sf;
unsigned int i;
uint32_t words[10];
if (len != 64) {
gpsd_report(LOG_PROG,
"ITALK: bad SUBFRAME (len %zu, should be 64)\n", len);
return 0;
}
flags = (ushort) getleu16(buf, 7 + 4);
prn = (ushort) getleu16(buf, 7 + 6);
sf = (ushort) getleu16(buf, 7 + 8);
gpsd_report(LOG_PROG, "iTalk 50B SUBFRAME prn %u sf %u - decode %s %s\n",
prn, sf,
flags & SUBFRAME_WORD_FLAG_MASK ? "error" : "ok",
flags & SUBFRAME_GPS_PREAMBLE_INVERTED ? "(inverted)" : "");
if (flags & SUBFRAME_WORD_FLAG_MASK)
return 0; // don't try decode an erroneous packet
/*
* Timo says "SUBRAME message contains decoded navigation message subframe
* words with parity checking done but parity bits still present."
*/
for (i = 0; i < 10; i++)
words[i] = (uint32_t)(getleu32(buf, 7 + 14 + 4 * i) >> 6) & 0xffffff;
return gpsd_interpret_subframe(session, prn, words);
}
/*
* decode MID 0xE0, GPS Subframe data
*
* len 33 bytes
*
*/
static gps_mask_t sky_msg_E0(struct gps_device_t *session,
unsigned char *buf, size_t len UNUSED)
{
int i;
unsigned int prn; /* GPS sat PRN */
unsigned int subf; /* subframe 1-5 */
/* the words are preprocessed, not raw, just the 24bits of data */
uint32_t words[10]; /* subframe 1-5 */
if ( 33 != len)
return 0;
prn = (unsigned int)getub(buf, 1);
subf = (unsigned int)getub(buf, 2);
for ( i = 0; i < 10; i++ ) {
words[i] = (uint32_t)getbeu24(buf, 3 + (i * 3));
}
gpsd_log(&session->context->errout, LOG_DATA,
"Skytraq: 50B MID 0xE0: prn=%u, subf=%u\n",
prn, subf);
return gpsd_interpret_subframe(session, prn, words);
}
