Current implementation saves s->drift as an offset between current clock
frequency and the remote clock frequency calculated on first two samples.
Locked state of the PI servo assumes the s->drift holds the history
of clock frequency difference scaled by s->ki * weight.
As a result the lock needs more time to stabilize when the frequency
offset is very large (ex. set to extreme values with phc_ctl) or may
totally prevent servo from correctly locking.
This patch fixes the s->drift when entering the stable state to hold
the scaled drift.
Signed-off-by: Maciek Machnikowski <mac...@machnikowski.net>
---
pi.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/pi.c b/pi.c
index 4a96a5b..bc38073 100644
--- a/pi.c
+++ b/pi.c
@@ -120,6 +120,7 @@ static double pi_sample(struct servo *servo,
*state = SERVO_LOCKED;
ppb = s->drift;
+ s->drift *= (s->ki * weight);
s->count = 2;
break;
case 2:
--
2.30.2
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