WDT feeding in the background, is this a good idea?


  • Pybytes Beta

    I want to keep my WDT fed but I would rather not write wdt.feed() all over the place. Is the code below a good idea or will it negate the purpose of having a WDT?

    My gut tells me this is wrong but I don't know enough to be sure.

    class WDT(object):
        def __init__(self, timeout = 10000):
            from machine import WDT
            self.wdt = WDT(timeout)
    
    
        def feeder_func(delay, id):
            from time import sleep
            while True:
                sleep(delay)
                self.wdt.feed()
    
    
        # TODO How do you kill a thread?
        def start()
            import _thread
            _thread.start_new_thread(feeder_func, 0)
    
    
        def stop(self):
            self.wdt.stop()
    

    Usage:
    >>> wdt = WDT()
    >>> wdt.start() # Being fed in the background...
    >>> wdt.stop()


  • Pybytes Beta

    I will stop the WDT just before deep sleep, and waking from sleep requires a reset, so it's not looped for me. main.py can take anywhere from a few seconds to several minutes to execute, so I don't know the maximum duration ahead of time.

    It would seem I would need to feed it all over the place, so I'll just fire up my copy and pasting.



  • @BetterAuto If you use deepsleep that is also some kind of loop. The way I use the WDT is to check if it can finish the loop, so 1 feed at the end. This assumes you somewhat know a maximum duration the loop can take. So I would just put it before putting the device to sleep. That way, if it hangs it will re-run the program until it succeeds.


  • Pybytes Beta

    I don't have a main loop. I have a main.py that executes once then the board goes back to sleep. So this would catch what you believe is the most common failure, that's good.

    Is there a guideline for how often to slip your feeders into the code? Before every statement? Every tenth statement? Only before expensive operations? Something else?



  • Why not just put it once in your main loop?
    Anyway, I've notifced crashes/freezes happen due to memory errors (if the rest of your code is well written). So the thread will also stop working when this happens, and the board will reset.


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