|Re: [chrony-users] Newbie requesting help|
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Thanks for the info Bill. I am not sure I understand all of it, so I'll
On 03/21/2016 02:39 PM, Bill Unruh wrote:
Not sure why you want to do it this way. You say that you can use an
interrupt. Have that interrupt read the system clock and output that
the device (eg /dev/clock). Then you have to make sure that the system
is, initally, within .25 sec of the UTC.
I was saying that /dev/clock would be the reference clock's vote for the
current time. By saying that /dev/clock can be used for the pps result,
are you implying that I don't need the reference clock's vote for the
time at all? Then how do I know what absolute time any PPS signal means?
So the Linux system time doesn't get a 'vote'? Its time is not an
'input' to chrony at all???? Sorry I am not understanding this.
Only one vote is needed. And you only have one vote-- both times are
equivalent-- they come from the same source: your clock.
GPSD grabs and interrupt, which tells it when the time on the exact
And it grabs the second source to tell it which second that is. You
already have that.
I do? I am not following. Could you try to map by reference clock C to
a GPS device, in terms of its value and pps outputs?
So i do or do not need 2 shm structs? If I do, how do I fill in the
clock and receive members of the two?
A ntp packet is four timestamps. When the request was sent, when the
was received by the remote clock, when the time was sent out by the
clock, and when the time was received by the local system. In your
remote system and the local system are the same. ntp ( which chrony
also uses) determines the offset of your local system by
(t1+t4-(t2+t3))/2 Thus t2 and t3 should be the "on the second" times,
and t4 the system time when the pulse comes in.
This will give a delay of 0, and an offset which is how much the local
off from UTC.
Your accuracy will now depend entirely on the accuracy of that clock
Quite sure. I am under water for hours at a time. My GPS device isn't
one that works under water. Maybe a more expensive model does.
Are you sure you cannot just use gps time?
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