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Check sample time stamps in drift calculation.

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Before calculating the clock drift in the PI servo, make sure
the first sample is older than the second sample to avoid getting
invalid drift or NaN.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
This commit is contained in:
Miroslav Lichvar 2013-02-05 17:36:10 +01:00 committed by Richard Cochran
parent a41e9f8c8c
commit 5667ab5d30
1 changed files with 6 additions and 0 deletions
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6
pi.c
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@ -73,6 +73,12 @@ static double pi_sample(struct servo *servo,
s->offset[1] = offset;
s->local[1] = local_ts;
/* Make sure the first sample is older than the second. */
if (s->local[0] >= s->local[1]) {
s->count = 0;
break;
}
s->drift += (s->offset[1] - s->offset[0]) * 1e9 /
(s->local[1] - s->local[0]);
if (s->drift < -s->maxppb)