Well I've tried several things in keeping with this kind of thing too, but
after a lot of wasted effort, I realized that the best solution is to write
critical variables periodically to a SAFE area and then go get them when
you power up. The cheapest way to do this is with a FRAMTRON I2C serial
memory, you can write to them often without a problem. Just write critical
variables into it say, every minute.

I'd tried many elaborate schemes, one in which I post a byte that indicates
which routine I am running normally (which is handy when diagnosing a
broken or in production troubleshooting), but when the WDT triggers,
something is WRONG and the data is meaningless.

--Bob


At 01:21 PM 7/14/2003 +0200, you wrote:
> > I think this is my misunderstanding of WDT.
> >
> > If there is a product which is used in industrial area where
> > there are pumps, and other machines that could mess up the
> > operation of the software in a uc, how would one make a
> > realiable product?
> >
> > In my case, the product I am working on works automatically
> > until stopped.  The user only needs to hit start and it does
> > the rest.  When there is pump/motor next to the unit, if it
> > strong enough, it causes the sofware to restart or do weird
> > stuff.  How could I prevent this?  I though I could use the WDT.
>
>my preference, in this order:
>1. try to get rid of the root cause: more shielding, decoupling, do
>somethiung about the motor itself, etc.
>2. design your system so that it can start again without the user
>noticing. if your system does time-sequencing things this might be
>difficult, but for a system that periodically gets its setpoints over
>some comms you could just wait for the next message
>3. if things still go wrong you might start again from eeprom values,
>provided that these are not corrupted. so store 3 times, and use
>brown-out reset
>
>Wouter van Ooijen
>
>-- -------------------------------------------
>Van Ooijen Technische Informatica: www.voti.nl
>consultancy, development, PICmicro products
>
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