Re: [Tinyos-help] TimerC filling task queue?

[Matt Thompson]

It is too bad TinyOS doesn't context switch between tasks ;) About the modifications to TimerB's divisor, it breaks DCO calibration unless you change the TARGET_DELTA from 2048 to 256 in MSP430DCOCalibM.nc. With this configuration, I can use the Timer module properly with long operations (ECDSA), and have yet to see any issues with peripherals (CC2420, STM25 flash, UART, external iButton). Why would we want the extra interrupt load of the timer overflowing every 2 seconds?  Would that not also mean that it has to wake up from LPM every 2 seconds to process the interrupt (I have yet to look into LPM at all..so I'm completely unsure of its operation). Cheers, Matt Prabal Dutta wrote: Matt, ECDSA is a pretty long running operation and we've seen similar problems with other algorithms like RSA and FFT that can have long running times. You best bet for getting it to work in TinyOS without screwing with the task queues or other internals is to write your algorithm so it operates in multiple phases, with each phase short enough to avoid overflowing the timer. The easiest way to do this, like the referenced thread states, is to iterate through long loops in pieces. You should avoid the temptation to break the system model (short tasks) even if you can get it to work in a particular case. The reason is that the rest of the system is built on top of that assumption and you risk causing unintended side effects. - Prabal On 2/6/06, Matt Thompson <[EMAIL PROTECTED]> wrote: Are there any inherent problems with setting the TimerB divisor to 8 in MSP430ClockM.nc (by adding ID_DIV8 in MSP430ClockInit.defaultInitTimerB()), and changing "milli*32" to "milli*4" in TimerM.nc? This should make TimerB work at 4khz, overflowing the 16bit counter approx every 16 seconds. Cheers, Matt Cory Sharp wrote: On 2/5/06, Michael Schippling <[EMAIL PROTECTED]> wrote: Oh, now here is an interesting bit of trivia.... TimerC overflows a 16bit count every 2 sec. But the interface has a resolution of 1ms, and there has been talk about what the max timeout when using the i/f is? For the MSP430 in tinyos-1.x, the max timeout is something like 2^26 or 2^27 milliseconds -- about 18 hours. And the lack of wiring vs not including in the config file...hmmm? Is the Timer always started in StdControl.init() even if not used? TimerM.nc is wired to a counter overflow interrupt in the MSP430, which is handled regardless of StdControl. I've probably missed a really important piece of documentation...Can you elucidate a bit? thx MS Cory Sharp wrote: None of the drivers in TinyOS are written to be able to sustain a task taking long seconds or more to complete. Blocking the task queue for a long time is bad. Read the discussion pointed to my Michael. You must split your long task into multiple tasks, each task incrementally doing more processing. For the MSP430 TimerC in particlar, every two seconds, for each overflow of a 32khz 16-bit counter, a task is posted to process that overflow. The current overflow MUST be processed before the next overflow occurs. For a healthy, reactive system, I recommend no one task take longer than, say, tens of milliseconds to complete. Cory On 2/5/06, Matt Thompson <[EMAIL PROTECTED]> wrote: Hi, It appears that TimerC is filling the task queue while a long task is running (ie Elliptic Curve DSA signature verification). After the ECDSA task completes, the telosb is unable to process any more tasks. Is there a way to stop the timer from posting tasks before a long operation is started? It seems that even if I do not start the timer (and it is not wired to StdControl), the task queue still fills up. I have to completely remove it from the configuration for this behaviour to disappear. Why does the mote not continue to process the task queue after the long task completes, and then allow me to post more tasks when some of them have completed? Has anyone else expereienced similar behaviour? Cheers, Matt _______________________________________________ Tinyos-help mailing list Tinyos-help@Millennium.Berkeley.EDU https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help _______________________________________________ Tinyos-help mailing list Tinyos-help@Millennium.Berkeley.EDU https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help _______________________________________________ Tinyos-help mailing list Tinyos-help@Millennium.Berkeley.EDU https://mail.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help

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