Re: [ECOS] Change system tick during runtime

[Gary Thomas <gary at mlbassoc dot com>]

On Wed, 2003-10-01 at 06:55, Daniel Lidsten wrote:
> Hi,
> 
> Is there any way of changing the system tick during runtime? I have made
> a quick test by letting an application provided variable be used when
> setting the decrementer in the HAL_CLOCK_*-functions. This will make the
> system generate tick more or less often depending on the value set.
> However, the drawback is that the system expects that we have a
> heartbeat of 100Hz and that will differ when changing the decrementer.
> Is there any way to get around this? Is there any way to change the
> CYGNUM_HAL_RTC_DENOMINATOR during runtime so that the change will affect
> every file that use it? I want to be able to have 10000 ticks per second
> but then i also need to let the system know that we have 10000 ticks per
> seconds so that not all timeouts and stuff gets all confused.
> 

Are you sure that you want the system clock to run at this high of
a frequency?  That means that every 100us you are going to execute
the clock handler, which oft times ends up running the scheduler, etc.
Unless you're on a blazingly fast platform, this seems like too much
overhead.

If you just want higher granularity timers or interrupts, how about 
using a second timer for this purpose?

As for changing the clock frequency on the fly, I don't think eCos 
is set up for this, nor (IMO) is it a good idea.

Maybe if you explain a little more the *why*, we can give you some
ideas on the *how*.

-- 
Gary Thomas <gary@mlbassoc.com>
MLB Associates


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