| Re: [chrony-users] Refclock Integration Advice |
[ Thread Index |
Date Index
| More chrony.tuxfamily.org/chrony-users Archives
]
- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] Refclock Integration Advice
- From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
- Date: Mon, 30 Nov 2020 16:11:53 +0100
- Authentication-results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlichvar@xxxxxxxxxx
- Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606749118; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=cuy2Z/7YW6Pdtv8TjZxUE0f9NMJWaUMTB+JBImu72i8=; b=a4ujEGiWebKd72+bTHkwZqeMy/47T+ofmaqlGFv7JOq08mJCgsenk/ey0SNLeuWCX20ECD TPQ+CNP8fnn8HT2/UYnBgi4eJjmBcbDBQrBuk9CULtQV2vCKZb1wU0BZ1066rFhF/bue08 lcJsF7cowkvwK/87s3IU/FYwiT/QA8A=
On Mon, Nov 30, 2020 at 03:03:10PM +0000, Chang, Benjamin wrote:
> So I managed to switch it to a 50% duty cycle PPS, and it appears to take every pulse now. The LastRX floats between 0 and 2 (seemed like 20 us is too short a pulse).
>
> However, now when I look at the measured offsets, it seems to greatly vary from 100s of ns to 10s of us. Shouldn't it be consistent? According to the datasheet of my PPS (the syncserver S650), it should have ~15 ns accuracy and resolution. When I scoped it on an oscilloscope, it was consistent and not varying.
>
> Here is my conf file setup
> My ntp server setting: minpoll -6 maxpoll -6
> My PPS: poll 0 prefer trust pps width 0.5
If you use a serial port for the PPS, the stability will depend on how
stable is the interrupt delay. A stability in tens of microseconds is
not unusual. You may get better results if you disable all
power-saving states and set a fixed frequency for the CPU.
If you increase the chrony poll to 3 or 4, the PPS samples will be
filtered using a median filter and that should help with the outliers.
--
Miroslav Lichvar
--
To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "unsubscribe" in the subject.
For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "help" in the subject.
Trouble? Email listmaster@xxxxxxxxxxxxxxxxxxxx.