[riot-devel] Question about hwtimer_now implementation..
hauke.petersen at fu-berlin.de
Wed Oct 15 11:51:15 CEST 2014
I try to answer your questions to the best of my knowledge...
On 14.10.2014 22:06, Joakim Gebart wrote:
> I have some other hwtimer questions too:
> Is the hardware timer module expected not to halt when the CPU is
> entering low power modes (STOP etc.)?
I am actually not sure this specified (yet).
> Is the hwtimer module expected to be able to keep any particular precision?
There is no official RIOT-wide requirement on hwtimer precision so far.
There are however some device (i.e. radio) drivers, that do need a
certain precision. Unifying this over all platforms is however still
work in progress.
> Does the hwtimer module need to be able to wake the CPU from sleep?
Depends on the answer of your first question...
>> But as Ludwig mentioned, hwtimer_arch_now() is expected to return this free running counter value.
> What are the assumptions made by the OS on this timer implementation?
> Is it expected to not overflow in less than X seconds? There has been
> some discussions on the mailing list and the Github tracker about some
> platforms with only 16 bit counters for timers and the problems that
> comes with it.
In general the hwtimer is allowed to overflow and there is no
specification on the period this happens. Providing a timer abstraction
that can cope with different overflow intervals and different
timer-widths is something we are working on, though.
>> Best, Thomas
>> devel mailing list
>> devel at riot-os.org
> Best regards,
> devel mailing list
> devel at riot-os.org
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