[ntp:questions] NTP on CubieBoard
nomail at example.com
Tue Oct 14 07:30:12 UTC 2014
Brian Inglis <Brian.Inglis at SystematicSw.ab.ca> wrote:
> The SoC implementation seems to be an AllWinner Technology A20
> designed for low power mobile uses.
> There is a lack of tech docs about these implementations available.
> When I see low power mobile, I expect power and speed throttling,
> so usability for NTP will depend on how well you can disable those
> features to run with power always on.
It does not really matter if the CPU is sleeping, as long as it can
wakeup on an interrupt quickly and as long as there is a real time
counter (e.g. a clock cycle counter) that ticks at a constant rate.
The only thing required to run realtime is an interrupt routine that
reads the content of the highres timing counter when an input line
changes state. All the other things can run at kernel and user level
at varying speed and priority, and the result will still be good.
> But there is a reference to enabling Cubian Kernel PPS.
> Whether that works or well seems to be answerable only by buy it and try it.
I will do the experiment, indeed I see that PPS is enabled in the config
after some change so maybe it works out of the box.
> You may be better targeting a non-mobile platform or one of the Intel
> embedded Linux boards designed to address the plethora of ARM boards.
The fact that is is low-power helps us. But we need to keep the clock
accurate. When this is not achievable we can still use the board for
only a receiver, but not for a transmitting station.
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