[ECOS] Changing system timer resolution

Jurica Baricevic jura@INTESIS.hr
Sun Nov 18 19:05:00 GMT 2001

Grant Edwards wrote (Wednesday, November 28, 2001 17:28):
> I've gotten repeated requests from customers for different
> (generally smaller) system timer resolutions.  Changing the
> timer resolution is easy enough, but doing so breaks things
> things since a lot of application level code (system tests, TCP
> stack, DHCP task, etc.) depends on the assumption that a system
> timer tick is 10ms.  [This assumption seems like a fairly
> fundamental flaw for RTOS application code.]
> It would be awfully nice if there were a simple way for an
> application to determine the system timer tick resolution (e.g.
> macros/functions to convert back and forth between
> seconds<->ticks and ms<->ticks).  I know this information is
> available, but it's buried pretty deeply and is difficult to
> use.

I absolutely agree with the statement above. Currently, I am using some
"home-made" calculations and macros in my applications (i.e. for
cyg_thread_delay()) and they look quite awkward. Some 'easy to use'
conversion between real time and system tick in any form (API, macro) would
be quite useful.

Also, it would be nice to have some high-resolution performance counter for
more precise time handling. For example, microsecond handling is quite
common in today's RTOS applications. The high-resolution counter shouldn't
be limited by system timer tick resolution, but with the underlying hardware
clock resolution.

> Things like TCP and DHCP could then be written so that they
> work with any system tick resolution.
> If there were macros to convert between "real-world" time and
> system ticks, how many places would those need to be inserted
> for an eCos system to "just work" when the system timer
> resolution is changed?
> Would a change like this make it into the standard source tree?

I believe that eCos community would benefit from this change.

> If not, I don't think I want to fork my own version and have to
> support it ad inifinitum -- I'll just have to tell those
> customers they're out of luck if they don't like 10ms timer
> ticks.
> --
> Grant Edwards
> grante@visi.com

Best regards,
Jurica Baricevic

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