[Tinyos-help] Can events preempt tasks?

[Chalermphol Thammapalerd]

Yes, it simply toggle the LED.
Note that I'd be happy to share my code because it's very important part of
the system to prove.

Regards,
Chalermphol


On 7/4/06, Ravi Prasad <ravi4edu at yahoo.com> wrote:
>
>
> Is the event B is doing its job inside an ISR  or a lower level event
> called from ISR ?? OR it is trying to post a task for its job??
>
> It seems your's is the second case.
>
> I suggest you to simply toggle an LED in your event.
>
>
> *Chalermphol Thammapalerd <t.chalermphol at gmail.com>* wrote:
>
> Hi folks,
>
> Thanks for the answer, but I'm sorry for my vague question.
> Ravi, In your excellent case, the task is absolutely preempted.
> But how about the unfinished task(actually I mean to the never-finish
> task)?
> My test is,
>
> A. A never-finish task which is periodically posted
>    {
>    while(1) {
>    //do a thing
>    }
>    }
>
> B. Asynchronous Event
>     SomeExternalInterrupt.fired {
>     //do another thing
>     }
>
> In this case, B is able to generate the event to "do another thing" but
> only once and the mote seems like hang.
> I'm not sure if this kind of programming should never be used or there're
> some trick(s) to avoid this deadlock? or is it a deaklock anyway?
>
> Regards,
> Chalermphol
>
> On 7/4/06, Ravi Prasad <ravi4edu at yahoo.com> wrote:
> >
> >
> > Make an application as follows:
> >
> > 1. Implement a task
> >        task free_run_timer(){
> >           a. initiate a  _free_  runing timer to count.
> >           b. wait a fixed amount of time.
> >           c. stop timer.
> >           d. Read and send the value of timer/counter to radio/uart.
> >        }
> > **Do not use any atomic statement in this task.
> >
> > schedule a timer to post this task periodically.
> >
> >
> >
> > 2. Implement an event which is having a fixed delay in it. A short cut
> > is to use the UART as an interrupt source. Everytime you send a character to
> > mote from a PC by serial port it will generate an interrupt and thus an
> > event.Remember to use the uart/radio interface in your application and
> > start it properly.
> >
> >
> > Now if there is no event generated (do not send any radio or UART packet
> > to mote) then the counter value will be same every time. When you generate
> > an event(possibly by sending a uart packet) you can easily see the counter
> > value to be changed which proves the task was preemted to serve the event.
> > **Probably you will have to genererate a series of events so that few of
> > them fall inside the time when task is running.
> >
> >
> >
> > *Chalermphol Thammapalerd <t.chalermphol at gmail.com >* wrote:
> >
> >  Hi,
> >
> > I tried to prove one of the TinyOS concept, "Events preempt tasks, tasks
> > do not", by using external event to preempt unfinished task.
> > However, the task is not seem to be preempted at all.
> > Are there any example(s) that prove this concept?
> >
> > Regards,
> > Chalermphol
> > _______________________________________________
> > Tinyos-help mailing list
> > Tinyos-help at Millennium.Berkeley.EDU
> > https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
> >
> >
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Tired of spam? Yahoo! Mail has the best spam protection around
> > http://mail.yahoo.com
> >
>
>
>  ------------------------------
> Talk is cheap. Use Yahoo! Messenger to make PC-to-Phone calls. Great rates
> starting at 1¢/min.
> <http://us.rd.yahoo.com/mail_us/taglines/postman7/*http://us.rd.yahoo.com/evt=39666/*http://messenger.yahoo.com>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.millennium.berkeley.edu/pipermail/tinyos-help/attachments/20060704/4839d02c/attachment.htm