Re: [Oslib-devel] PIT... scheduler

[<luc...@em...>]

Hi Juras,

>   how to install a task scheduler? using pit_init(0,TMR_MD2,1) (from
>   the sources of xlib dir...) or by using events?
This is your choice ;) OSLib provides you the low-level functionalities
from xlib (l1_irq_bind() and pit_init()), or the higher level
functionalities from kl (the events). If you use events, you don't have
to care about programming the PIT, or explicitly setting an irq handler:
you simply call the event_post() interface (after calling event_init(),
of course ;), and it will do everything for you...

If you prefer the ``do it by yourself'' strategy, you can avoid using
events, and you can program the PIT and handle the PIT interrutp by
yourself... But this will be more complex, of course. 

> if using events, then the event handler must post another event,
> then exception 13 is generated...
Have a look at examples/scheddem.c: it does exactly what you need... And
it worked, last time that I checked ;-)

>   could you explain the parameters of pit_init? what mode should I
>   take, what channel, how to calculate appropriate const? I was
>   looking through the sources but the lack of comments...
pit_init(c, m, t) programs the PIT channel c to mode m and constant t.
The channel connected to the timer interrupt is channel 0 (i think ;),
and the modes that I generally use are mode 4 for generating periodic
interrupts, and mode 2 for generating one-shot interrupts. The value of
the time constant can be computed as <time in us> * 1197 / 1000.
Everything is explained a little bit better in the Intel docs ;)
Anyway, if you use events you do not have to care about these details.

			Luca
-- 
_________________________________________________________________________
Add this to your signature, if you think it is important
                       N O   W A R ! ! !