[avr-chat] Re: mega644 resetting continuously

[Steve Franks]

On 1/29/07, Daine Mamacos <address@hidden> wrote:
> Hey, I tumbled upon your post, and I have EXACTLY the same problem.
>
> I've disabled watchdog timers, in software and on the fuses. I also ram
>
> Stuff out on the UART, and it resets in the middle of pushing a string out
>
> On UART if it's too long. It doesn't seem to matter what I do, I can't stop
>
> It from resetting.
>
> I know it's been a while, but have you managed to sort this issue out?
>
>
>
> Any help would be appreciated. Thanks
>
> Daine Mamacos.
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Daine,

First, it was one of those problems that was never really 'fixed' -
just sort of went away slowly.

It seemed to be somewhat related to the jtag-ice - I recall it seemed
to behave differently wether the reset pin on the jtag was connected
(I find the way the jtag holds it in reset annoying, so I have a
special dongle with no reset line).  So it could have been noise on
the reset.

It also seemed highly dependant on how many globals I had in the code
above main() - moving everything into locals in main helped
tremendously.

I don't have the problem at all on the new 4.1.1 compiler, probably
just because it optimizes better - but if you're on windows, you'll
have to wait until the next winavr release.

Also, on all the new devices, simply calling wdt_disable() is
insufficient to disable the wdt (mentioned in the fine print somewhere
in wdt.h - thanks to Joerg for pointing it out in my hour of need).  I
suspect 644 falls under this heading.  Instead add this above main (if
you haven't already, of course):

void EarlyInit(void) __attribute__ ((naked)) __attribute__ ((section
(".init3")));
void EarlyInit(void)
{
        MCUSR = 0;
        wdt_reset();
        wdt_disable();
}

Best of luck,
Steve

--
Steve Franks, KE7BTE
Staff Engineer
La Palma Devices, LLC
http://www.lapalmadevices.com
(520) 312-0089