Clear WDRF flag and set WDCE before enabling watchdog

Makefile

@@ -50,13 +50,8 @@ DEPENDS   := $(FILES:%.c=$(TMPDIR)/%.d)
 # AUXILIARY TARGETS (AND FUSE SETTINGS)
 # ==============================================================================
 
-# .PHONY: all
-# all: flash
-
-.PHONY: run
-run: $(TARGET)
-	$(E) "[SIM] $<"
-	$(Q) $(SIM) -m $(MCU) -f $(FREQ) $<
+.PHONY: all
+all: flash
 
 .PHONY: flash
 flash: $(TARGET)
@@ -69,6 +64,11 @@ flash: $(TARGET)
 	       -U lock:w:0xFF:m      \
 	       -U flash:w:$<
 
+.PHONY: run
+run: $(TARGET)
+	$(E) "[SIM] $<"
+	$(Q) $(SIM) -m $(MCU) -f $(FREQ) $<
+
 .PHONY: clean
 clean:
 	$(E) "[REM] $(TARGET)"

src/common/watchdog.c

@@ -36,8 +36,17 @@ void WDT_Enable(void)
 	// set. Once written to one, hardware will clear
 	// WDCE after four clock cycles.
 
+	// Setting WDCE before enabling the watchdog should
+	// not be necessary according to the data sheet but
+	// it does not seem to work otherwise.
+
+	// Disable interrupts
+	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+		MCUSR &= ~BIT(WDRF);
+		WDTCSR = BIT(WDCE) | BIT(WDE);
 		// 00001111: Watchdog enabled, 2sec timeout
 		WDTCSR = BIT(WDE) | BIT(WDP2) | BIT(WDP1) | BIT(WDP0);
+	}
 }
 
 void WDT_SetTimeoutFlag(byte flag)
@@ -65,13 +74,13 @@ void WDT_SetTimeoutFlag(byte flag)
 
 	// Disable interrupts
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+		WDT_Reset();
 		WDTCSR = BIT(WDCE) | BIT(WDE);
 		// Set new timer prescalar flag
-		WDTCSR = (WDTCSR & 0xC8) | flag; // C8=11001000
+		WDTCSR = BIT(WDE) | flag;
 	}
 }
 
-// XXX: COMMENTS UPDATED!
 bool WDT_HasTriggered(void)
 {
 	bool isreset;
@@ -109,6 +118,7 @@ void WDT_Disable(void)
 
 	// Disable interrupts
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+		WDT_Reset();
 		WDTCSR = BIT(WDCE) | BIT(WDE);
 		WDTCSR = 0;
 	}

src/main.c

@@ -57,14 +57,6 @@ static int Init(void)
 
 	Info("Initializing...");
 
-	// FIXME: Something is wrong here:
-	// - AVRDUDE sometimes fails to verify flash.
-	// - UART sometimes stops working.
-	// - External crystal problems?
-	// - Power supply problems?
-	// - Wrong fuses? Unlikely.
-	// - Bootloader problems?
-
 	// The watchdog timer is clocked from a separate
 	// on-chip oscillator which runs at 1 MHz. Eight
 	// different clock cycle periods can be selected