I am using atmega 128 for a smart vehicle tracker. I am trying to use watchdog timer for this controller.But problem is that I have found the maximum watchdog reset time is 2 seconds. I need watchdog reset time 8 seconds. Now what can I do ?
There is no way you can make the Watchdog timer longer on Atmega 128. It is max 1.8 sec if you set all 3 bits of Timer Prescaler.
For Atmega 328 the max watchdog time is 8 sec and longer time can be achieved using watchdog interrupt and count up (or down) until you want a reset and then force the reset by setting the shortest watchdog timer.
Atmega 128 doesn't support watchdog interrupt, so the trick with interrupt can't be used.