| Re: [chrony-users] RTOS with Chrony/GPS - worth considering ? |
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- To: chrony-users@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-users] RTOS with Chrony/GPS - worth considering ?
- From: Laura Smith <n5d9xq3ti233xiyif2vp@xxxxxxxxxxxxx>
- Date: Mon, 07 Mar 2022 10:03:56 +0000
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On Monday, March 7th, 2022 at 09:59, Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:
> On Sat, Mar 05, 2022 at 12:39:57PM +0000, Laura Smith wrote:
>
> > I'm planning to setup a GPS backed timeserver, and my understanding is that the "best" way to do this currently is to use GPSd + chrony to get GPS + 1PPS.
> >
> > Reading up a little on the details, my understanding is that the 1PPS part works by generating interrupts on the server either via GPIO or COM Port DCD pin.
>
> The best way would be hardware timestamping of PPS, e.g. by connecting
>
> the signal to one of the SDPs on the Intel I210 as described here:
>
> https://chrony.tuxfamily.org/examples.html#_server_using_reference_clock_on_nic
>
> If that is not possible, you could use a polling variant of the GPIO
>
> PPS driver to at least avoid the interrupt latency:
>
> https://github.com/mlichvar/pps-gpio-poll
>
> > This then raised the question in my mind as to whether choice of OS was important. In particular whether the use of an RTOS platform (e.g. FreeRTOS) would be beneficial given that the internals of na RTOS mean it is better setup for dealing with interrupts in an efficient and timely manner ?
>
> I have no experience with that. Does chrony run on FreeRTOS?
Thank you for the food for thought Miroslav, appreciate it. I will do some reading up on the links provided.
Regarding your last question, I haven't tried (yet ?) but there certainly seems to be a how-to on their website: https://www.freertos.org/sntp/setting-up-an-ntp-server.html
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