Here is an example sketch to make the watchdog work, plus see the watchdog section of Sam3x datasheet :
#define WDT_KEY (0xA5)
/********************************************************************************
extern "C" void _watchdogDefaultSetup (void) { WDT_Disable (WDT); }
void watchdogSetup (void) __attribute__ ((weak, alias("_watchdogDefaultSetup")));
*********************************************************************************/
/*This function is called from init(). If the user does not provide
this function, then the default action is to disable watchdog.
This function has to be overriden, otherwise watchdog won't work !! */
void watchdogSetup(void) {
/*** watchdogDisable (); ***/
}
//void watchdogDefaultSetup (void) { }
//void watchdogSetup(void) { watchdogDefaultSetup ();}
void setup()
{
// Enable watchdog.
WDT->WDT_MR = WDT_MR_WDD(0xFFF)
| WDT_MR_WDRPROC
| WDT_MR_WDRSTEN
| WDT_MR_WDV(256 * 2); // Watchdog triggers a reset after 2 seconds if underflow
// 2 seconds equal 84000000 * 2 = 168000000 clock cycles
/* Slow clock is running at 32.768 kHz
watchdog frequency is therefore 32768 / 128 = 256 Hz
WDV holds the periode in 256 th of seconds */
Serial.begin(250000);
uint32_t status = (RSTC->RSTC_SR & RSTC_SR_RSTTYP_Msk) >> RSTC_SR_RSTTYP_Pos; // Get status from the last Reset
Serial.print("RSTTYP = 0b"); Serial.println(status, BIN); // Should be 0b010 after first watchdog reset
}
void loop()
{
//Restart watchdog
WDT->WDT_CR = WDT_CR_KEY(WDT_KEY)
| WDT_CR_WDRSTT;
Serial.println("Enter the main loop : Restart watchdog");
GPBR->SYS_GPBR[0] += 1;
Serial.print("GPBR = "); Serial.println(GPBR->SYS_GPBR[0]);
delay(500);
while (true)
{
Serial.println("the software becomes trapped in a deadlock !");
delay(500);
/* If the software becomes trapped in a deadlock,
watchdog triggers a reset and software restarts with stored values
in General Purpose Back up Registers*/
}
}