[rtl-sdr][PATCH 2/2] rtl_fm: Add squelch timeout

The current squelch logic waits until the received signal drops below the squelch value and then continues the frequency scan. If there's any continuous transmission on the air, it will block the scanning process forever. This patch adds support for squelch timeout to prevent the scanner from locking forever to a single signal. Signed-off-by: Nikolay Dimitrov <picmaster(a)mail.bg> --- src/rtl_fm.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/src/rtl_fm.c b/src/rtl_fm.c index 04f08a2..51313d3 100644 --- a/src/rtl_fm.c +++ b/src/rtl_fm.c @@ -84,6 +84,8 @@ #define FREQUENCIES_LIMIT 1000 +#define SQUELCH_TIMEOUT 100 + static volatile int do_exit = 0; static int lcm_post[17] = {1,1,1,3,1,5,3,7,1,9,5,11,3,13,7,15,1}; static int ACTUAL_BUF_LENGTH; @@ -135,6 +137,7 @@ struct demod_state int squelch_conseq; int squelch_hits; int squelch_signal_rms; + int squelch_timer; int terminate_on_squelch; int downsample_passes; int comp_fir_size; @@ -762,6 +765,7 @@ void full_demod(struct demod_state *d) } } else { d->squelch_hits = 0; + d->squelch_timer++; } } @@ -830,10 +834,18 @@ static void *demod_thread_fn(void *arg) do_exit = 1; } - if (d->squelch_level && d->squelch_hits > d->squelch_conseq) { - d->squelch_hits = d->squelch_conseq + 1; /* hair trigger */ - safe_cond_signal(&controller.hop, &controller.hop_m); - continue; + if (d->squelch_level) { + if (d->squelch_hits > d->squelch_conseq) { + d->squelch_hits = d->squelch_conseq + 1; /* hair trigger */ + safe_cond_signal(&controller.hop, &controller.hop_m); + continue; + } + + if (d->squelch_timer >= SQUELCH_TIMEOUT) { + d->squelch_timer = 0; + safe_cond_signal(&controller.hop, &controller.hop_m); + continue; + } } pthread_rwlock_wrlock(&o->rw); @@ -972,6 +984,7 @@ void demod_init(struct demod_state *s) s->squelch_conseq = 10; s->terminate_on_squelch = 0; s->squelch_hits = 11; + s->squelch_timer = 0; s->downsample_passes = 0; s->comp_fir_size = 0; s->prev_index = 0; -- 1.7.10.4