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- To: "chrony-users@xxxxxxxxxxxxxxxxxxxx" <chrony-users@xxxxxxxxxxxxxxxxxxxx>
- Subject: RE: [chrony-users] Refclock Integration Advice
- From: "Chang, Benjamin" <Benjamin.Chang@xxxxxxxxxxxxxxx>
- Date: Mon, 30 Nov 2020 15:03:10 +0000
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- Thread-topic: [chrony-users] Refclock Integration Advice
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
My PPS is coming from my NTP server so they are in sync. Is maybe my ntp polling too high for chrony causing the accuracy to fall off? I was told that polling too often can decrease rate accuracy so maybe the offset recordings are cause the recorded accuracy is off?
Also noted regarding the pictures attachment. My apologies.
-----Original Message-----
From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
Sent: Thursday, November 26, 2020 3:11 AM
To: chrony-users@xxxxxxxxxxxxxxxxxxxx
Subject: Re: [chrony-users] Refclock Integration Advice
On Mon, Nov 23, 2020 at 03:26:31PM +0000, Chang, Benjamin wrote:
> Assuming that's right, somehow its overlapping itself? From the attached image (I drew red lines to help separate), the first and second asserts are the same, but the "clear"s are different. Shouldn't the first clear prevent the second assert from being 'behind'/earlier than the first clear? Somehow its stepping backwards in time?
The command is just reporting the last registered assert and clear events, separately. If an assert is missing, the same value will be reported multiple times.
If clear is more reliable, maybe you could use them for synchronization with the :clear option and correct the offset with the offset option?
Ideally, you would configure the GPS to make a longer pulse, or add a pulse stretcher.
BTW, if you need to post screenshots, please upload them somewhere first (e..g. imgur.com) and post just a link here. Thanks.
--
Miroslav Lichvar
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