Patch to prevent Reboot loop when using watchdog

utility/WatchdogAVR.cpp

@@ -8,31 +8,49 @@
 #include <avr/sleep.h>
 #include <avr/wdt.h>
 
+#if ARDUINO >= 100
+  #include "Arduino.h"
+#else
+  #include "WProgram.h"
+#endif
+
 #include "WatchdogAVR.h"
 
+void(* resetFunc) (void) = 0;
+
 // Define watchdog timer interrupt.
 ISR(WDT_vect) {
-    // Nothing needs to be done, however interrupt handler must be defined to
-    // prevent a reset.
+
+	if (_sleepy != _MAGIC_SLEEPY) {  
+		// Disable watchdog and soft reset
+		MCUSR = 0;
+		wdt_disable();	
+		resetFunc(); 
+		}	
+	_sleepy=0; // Terminate sleep mode
 }
 
 int WatchdogAVR::enable(int maxPeriodMS) {
     // Pick the closest appropriate watchdog timer value.
-    int actualMS;
-    _setPeriod(maxPeriodMS, _wdto, actualMS);
+	int actualMS;
+    _setPeriod(abs(maxPeriodMS), _wdto, actualMS);
     // Enable the watchdog and return the actual countdown value.
     wdt_enable(_wdto);
+    if (maxPeriodMS<0) WDTCSR |= (1<<WDIE);             // Enable only watchdog interrupts.
+	_sleepy=0;
     return actualMS;
 }
 
 void WatchdogAVR::reset() {
     // Reset the watchdog.
     wdt_reset();
+	_sleepy=0;
 }
 
 void WatchdogAVR::disable() {
     // Disable the watchdog and clear any saved watchdog timer value.
     wdt_disable();
+	_sleepy=0;
     _wdto = -1;
 }
 
@@ -70,6 +88,7 @@ int WatchdogAVR::sleep(int maxPeriodMS) {
 
     // Set full power-down sleep mode and go to sleep.
     set_sleep_mode(SLEEP_MODE_PWR_DOWN);
+    _sleepy=_MAGIC_SLEEPY; // The only place where it should get this value
     sleep_mode();
 
     // Chip is now asleep!
@@ -86,7 +105,7 @@ int WatchdogAVR::sleep(int maxPeriodMS) {
 }
 
 void WatchdogAVR::_setPeriod(int maxMS, int &wdto, int &actualMS) {
-    // Note the order of these if statements from highest to lowest  is 
+	// Note the order of these if statements from highest to lowest  is 
     // important so that control flow cascades down to the right value based
     // on its position in the range of discrete timeouts.
     if((maxMS >= 8000) || (maxMS == 0)) {

utility/WatchdogAVR.h

@@ -1,6 +1,18 @@
 #ifndef WATCHDOGAVR_H
 #define WATCHDOGAVR_H
 
+
+// Allows the WDT ISR to know if it's called from the sleep function or if
+// a reset is to be performed.
+// The 16 bits holds a "magic value" to prevent reset. This is safer than 
+// using a boolean in case the memory gets trashed.
+// This is defined as global to allow access by the ISR
+
+#include <stdint.h>
+
+static uint16_t _sleepy;
+#define _MAGIC_SLEEPY ~0xDEAD
+
 class WatchdogAVR {
 public:
     WatchdogAVR():
@@ -44,4 +56,7 @@ class WatchdogAVR {
     int _wdto;
 };
 
+
+
+
 #endif