[ECOS] Changing system timer resolution

Grant Edwards grante@visi.com
Mon Dec 3 08:16:00 GMT 2001


On Mon, Dec 03, 2001 at 12:40:24PM +0000, Jonathan Larmour wrote:

> > > I think I'd probably accept a (carefully written) patch avoiding the
> > > problems I mention above.
> > >
> > 
> > What we can do now is add a simple convertor that takes a time in
> > seconds and nanoseconds and converts it to ticks. A convertor in the
> > opposite direction would be good for completeness, but is not as
> > useful. There are already such convertors in the POSIX package.
> 
> I thought we were talking about _sub_-tick resolution? And gettimeofday-ish
> functionality?

I think we're talking about several different things at this point:

 1) Changing the tick period and having everything "just work"
 2) Providing converter routines for use when you don't know at compile
    time what the tick period is.
 3) Providing sub-tick read-current-time resolution.
 4) Providing sub-tick event/alarm scheduling.

It sounds like 1) is already there, 2) isn't hard, 3) is already there.

However, 4) is hard if you try to use the eCos clock/timer system.  If
somebody really does need 4) the easiest thing may be to use a dedicated
hardware timer and a custom driver that maintains a linked list of
delay/event pairs.

-- 
Grant Edwards
grante@visi.com



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