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refclock: add option to filter wrong pulse edges

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Add width option to the refclock directive to set expected width of
pulses in a PPS signal. The width adds a limit for the maximum offset
and root distance in order to reject PPS samples from wrong events, e.g.
PHCs which cannot be configured to timestamp only rising of falling
edges.
This commit is contained in:
Miroslav Lichvar
2017-05-19 18:51:03 +02:00
parent eceb8d9937
commit 1ca099473f
3 changed files with 36 additions and 1 deletions
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29
refclock.c
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@@ -85,6 +85,7 @@ struct RCL_Instance_Record {
double offset;
double delay;
double precision;
double pulse_width;
SCH_TimeoutID timeout_id;
SRC_Instance source;
};
@@ -208,6 +209,7 @@ RCL_AddRefclock(RefclockParameters *params)
inst->delay = params->delay;
if (params->precision > 0.0)
inst->precision = params->precision;
inst->pulse_width = params->pulse_width;
inst->timeout_id = -1;
inst->source = NULL;
@@ -415,6 +417,27 @@ RCL_AddPulse(RCL_Instance instance, struct timespec *pulse_time, double second)
return RCL_AddCookedPulse(instance, &cooked_time, second, dispersion, correction);
}
static int
check_pulse_edge(RCL_Instance instance, double offset, double distance)
{
double max_error;
if (instance->pulse_width <= 0.0)
return 1;
max_error = 1.0 / instance->pps_rate - instance->pulse_width;
max_error = MIN(instance->pulse_width, max_error);
max_error *= 0.5;
if (fabs(offset) > max_error || distance > max_error) {
DEBUG_LOG("refclock pulse ignored offset=%.9f distance=%.9f max_error=%.9f",
offset, distance, max_error);
return 0;
}
return 1;
}
int
RCL_AddCookedPulse(RCL_Instance instance, struct timespec *cooked_time,
double second, double dispersion, double raw_correction)
@@ -476,6 +499,9 @@ RCL_AddCookedPulse(RCL_Instance instance, struct timespec *cooked_time,
return 0;
}
if (!check_pulse_edge(instance, ref_offset - offset, 0.0))
return 0;
leap = lock_refclock->leap_status;
DEBUG_LOG("refclock pulse offset=%.9f offdiff=%.9f samplediff=%.9f",
@@ -500,6 +526,9 @@ RCL_AddCookedPulse(RCL_Instance instance, struct timespec *cooked_time,
filter_reset(&instance->filter);
return 0;
}
if (!check_pulse_edge(instance, offset, distance))
return 0;
}
filter_add_sample(&instance->filter, cooked_time, offset, dispersion);