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Re: HAL_DELAY_US()


On 8/14/06, Gary Thomas <gary@mlbassoc.com> wrote:
Øyvind Harboe wrote:
> Going through my changes to eCos, I ran into HAL_DELAY_US().
>
> Does this function belong in the application or eCos?
>
> If it can be implemented in a correct manner that does not require any
> configuration, then I believe it belongs in the HAL.
>
> If it needs to be tuned to the hardware in question, then I believe it
> belongs in the application space.
>
> The implementation in EB40a is busted because it is not
> multithreading/interrupt safe.
>
>
> Ref. earlier discussions HAL_DELAY_US() should take *at least* that
> many us, there is no upper limit or requirement on precision as such.

IMO, HAL_DELAY_US() should not be used if interrupts or thread switches
can cause a perturbation.  It's *only* function is to provide very simple
timing when devices require it.  It should not be used for arbitrary delays,
certainly not in user/application code.  For that, use 'cyg_thread_delay()'

Agreed.


However, e.g. i2c bitbang relies on it and I do believe that a
consensus was reached to make it compulsory.

IMO, a HAL should have no implementation or a correct implementation.

EB40a has a broken implementation and that implementation should be
deleted or replaced.

--
Øyvind Harboe
http://www.zylin.com

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