Re: [avr-gcc-list] Watchdog wakeup from sleep mode?

[Artur Lipowski]

Josh Pieper wrote:
...
> Is there an easy way to work around this?  I'm working with an
> ATmega8535 and ATTiny26 at the moment, but I think the problem is
> applicable to most AVR devices.
It's easy, just put into source something like this:
void check_reset_cond() __attribute__ ((naked)) \
            __attribute__ ((section (".init3")));

void check_reset_cond()
{
        uint8_t mcusr = MCUSR;
        MCUSR = 0;
        if (mcusr & _BV(WDRF))
        {
                // avoid avr-libc initialization because
                // it is a watchdog reset
                main();
        }
        else if (mcusr & _BV(PORF))
        {
                // Power-on reset - do normal startup
        }
        else
        {
                // other reset source - power down device
        }
}

It works with devices which have WDRF status bit, but it can be extended 
for other just by using some global variable as a reset source flag (I 
usually use 2 bytes with "checkboard" pattern eg. 0xA55A, and _only_ if 
flag word has such value it means watchdog reset).

Regards,
--
Artur Lipowski