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tetra_burst_sync: fix bug resulting in no initial sync 

If we didn't find a SYNC in the first 4096 bits, we never found sync
at all.  This patch fixes it, we treat the trs->bitbuf as a ring buffer
and discard older bits if we get more than the buffer size (4096) bits.
This commit is contained in:
Harald Welte 2011-04-23 11:42:25 +02:00
parent 997abfd0d0
commit f91f994300
1 changed files with 21 additions and 10 deletions
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31
src/phy/tetra_burst_sync.c
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@ -35,29 +35,40 @@ struct tetra_phy_state t_phy_state;
void tetra_burst_rx_cb(const uint8_t *burst, unsigned int len, enum tetra_train_seq type, void *priv);
static void make_bitbuf_space(struct tetra_rx_state *trs, unsigned int len)
{
unsigned int bitbuf_space = sizeof(trs->bitbuf) - trs->bits_in_buf;
if (bitbuf_space < len) {
unsigned int delta = len - bitbuf_space;
DEBUGP("bitbuf left: %u, shrinking by %u\n", bitbuf_space, delta);
memmove(trs->bitbuf, trs->bitbuf + delta, trs->bits_in_buf - delta);
trs->bits_in_buf -= delta;
trs->bitbuf_start_bitnum += delta;
bitbuf_space = sizeof(trs->bitbuf) - trs->bits_in_buf;
}
}
/* input a raw bitstream into the tetra burst synchronizaer */
int tetra_burst_sync_in(struct tetra_rx_state *trs, uint8_t *bits, unsigned int len)
{
int rc;
unsigned int train_seq_offs;
int cpy_len;
DEBUGP("burst_sync_in: %u bits, state %u\n", len, trs->state);
/* First: append the data to the bitbuf */
if (sizeof(trs->bitbuf) - trs->bits_in_buf < len)
cpy_len = sizeof(trs->bitbuf) - trs->bits_in_buf;
else
cpy_len = len;
memcpy(trs->bitbuf + trs->bits_in_buf, bits, cpy_len);
trs->bits_in_buf += cpy_len;
make_bitbuf_space(trs, len);
memcpy(trs->bitbuf + trs->bits_in_buf, bits, len);
trs->bits_in_buf += len;
switch (trs->state) {
case RX_S_UNLOCKED:
if (trs->bits_in_buf < TETRA_BITS_PER_TS*2) {
/* wait for more bits to arrive */
DEBUGP("-> waiting for more bits to arrive\n");
return cpy_len;
return len;
}
DEBUGP("-> trying to find training sequence between bit %u and %u\n",
trs->bitbuf_start_bitnum, trs->bits_in_buf);
@ -96,7 +107,7 @@ int tetra_burst_sync_in(struct tetra_rx_state *trs, uint8_t *bits, unsigned int
case RX_S_LOCKED:
if (trs->bits_in_buf < TETRA_BITS_PER_TS) {
/* not sufficient data for the full frame yet */
return cpy_len;
return len;
} else {
/* we have successfully received (at least) one frame */
tetra_tdma_time_add_tn(&t_phy_state.time, 1);
@ -137,5 +148,5 @@ int tetra_burst_sync_in(struct tetra_rx_state *trs, uint8_t *bits, unsigned int
break;
}
return cpy_len;
return len;
}