How can you determine what caused a watchdog timer reset

[thinkpeace]

I'm using a watchdog timer on the Moetino, and when a WDT reset occurs, I would like to log it the the flash so I can keep a count of resets.

Is there a way in Setup() to determine of the Moetino was reset do to a watchgod timer reset?

Code Select Expand

void setup()
{
  Serial.begin(9600);

  if( reset_caused_by_watch_dog )  // <----- How can I do this?
   {
       Serial.println( "Reset was caused by watchdog");
   }
    wdt_enable(WDTO_1S);
}
 
void loop()
{
  // the program is alive...for now. 
  wdt_reset();
 

  doSomeStuff();
}

[Felix]

You can check the bits in the status register corresponding to those resets:

Code Select Expand

  byte statusReg = MCUSR;
  if (statusReg & _BV(WDRF))
  {
    Serial.println("WDT reset");
  }
  else if (statusReg & _BV(EXTRF))
  {
    Serial.println("External reset");
  }

But note that Obtiboot bootloader does this check itself and resets the MCUSR = 0

[thinkpeace]

Does this mean I would need to modify the bootloader to save the MCUSR state?

[Felix]

Probably.
You need to keep the MCUSR preserved (ie just comment out the line that resets it).
However it may be a good idea to reset it sometime early in your program.