[Tinyos Core WG] SchedulerBasic

[Kevin Klues]

You need to take a look at the implementations of the McuSleep.sleep()
functions for the msp430 and atm128 platforms.  The very last thing they do
just before putting the microcontroller to sleep is renable interrrupts.  If
you are using a new platform that has a different microcontroller, you need
to be sure that it has implemented its McuSleep.sleep() function this way.

Quoted from TEP115:
 "McuSleep.sleep() puts the microcontroller into a low power sleep state, to
be woken by an interrupt. This command deprecates the
__nesc_atomic_sleep()call of TinyOS
1.x. Note that, as the 1.x call suggests, putting the microcontroller to
sleep MUST have certain atomicity properties. The command is called from
within an atomic section, and MUST atomically re-enable interrupts and go to
sleep. An issue arises if the system handles an interrupt after it
re-enables interrupts but before it sleeps: the interrupt may post a task,
but the task will not be run until the microcontroller wakes up from sleep."

Kevin

On 2/5/07, Martin Leopold <leopold at diku.dk> wrote:
>
> Hi All.
> I seem to be having a problem with a simple test program (for my cc2430
> platform). I don't have any tasks and I echo a char back over the UART
> in interrupt context. If I loop forever in say in Boot.booted all is
> dandy, but if I let the system boot all the way, I don't seem to get to
> my interrupt handler.
>
> If I'm not mistaken, what happens after the system boots is, that it
> ends up in the taskLoop (below). If I'm reading this correctly then my
> system will loop here forever with no help of recovery since interrupts
> are off.
>
> Am I missing something obvious here or what? To me this doesn't seem
> right - sleep is called with interrupts off and there is no way to post
> a new task from an interrupt.
>
>
> command void Scheduler.taskLoop() {
> ...
> atomic {
>    while ((nextTask = popTask()) == NO_TASK)    {
>       call McuSleep.sleep();
>    }
> }
>
> If I look at the old "TOSH_run_next_task" from 1.x interrupts would be
> turned on in between calls to __nesc_atomic_sleep():
>
>   void TOSH_run_task() {
>     for (;;) TOSH_run_next_task();
>   }
>
>   bool TOSH_run_next_task () {
>     ...
>     fInterruptFlags = __nesc_atomic_start();
>      ...
>     __nesc_atomic_end(fInterruptFlags);
>     ...
>     func();
>     return 1;
>   }
>
> --
> Regards Martin Leopold.
> Dept. of Computer Science, University of Copenhagen
> http://www.diku.dk/~leopold
>
>
>
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>



-- 
~Kevin
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