Update module 'watchdog' to run on atmega1284p hardware

src/common/watchdog.c

@@ -6,103 +6,111 @@ void WDT_Enable(void)
 {
 	Info("Enabling watchdog timer...");
 
-	// WDTCR: Watchdog Timer Control Register
+	// WDTCSR: Watchdog Timer Control Register
 
 	// 7     6     5     4     3    2     1     0
-	// –   –   -   WDTOE  WDE  WDP2  WDP1  WDP0 
+	// WDIF  WDIE  WDP3  WDCE  WDE  WDP2  WDP1  WDP0
 
-	// When the WDE is written to logic one, the
-	// Watchdog Timer is enabled, and if the WDE is
-	// written to logic zero, the Watchdog Timer
-	// function is disabled.
+	// WDP3:0: Watchdog Timer Prescaler
+	// The WDP3:0 bits determine the Watchdog Timer
+	// prescaling when the Watchdog Timer is running.
+	// The different prescaling values and their
+	// corresponding time-out periods are
 
-	// WDP2, WDP1, WDP0: Watchdog Timer Prescaler
-	// The WDP2, WDP1, and WDP0 bits determine the
-	// Watchdog Timer prescaling when the Watchdog
-	// Timer is enabled. The different prescaling
-	// values and their corresponding Timeout
-	// Periods are:
+	// WDP3 WDP2 WDP1 WDP0   Cycles  Timeout5V
+	//    0    0    0    0       2K       16ms
+	//    0    0    0    1       4K       32ms
+	//    0    0    1    0       8K       64ms
+	//    0    0    1    1      16K      125ms
+	//    0    1    0    0      32K      250ms
+	//    0    1    0    1      64K      500ms
+	//    0    1    1    0     128K     1000ms
+	//    0    1    1    1     256K     2000ms
+	//    1    0    0    0     512K     4000ms
+	//    1    0    0    1    1024K     8000ms
 
-	// WDP2 WDP1 WDP0   Cycles  Timeout3V  Timeout5V
-	//    0    0    0      16K    17.10ms    16.30ms
-	//    0    0    1      32K    34.30ms    32.50ms
-	//    0    1    0      64K    68.50ms    65.00ms
-	//    0    1    1     128K     0.14s      0.13s
-	//    1    0    0     256K     0.27s      0.26s
-	//    1    0    1     512K     0.55s      0.52s
-	//    1    1    0   1,024K     1.10s      1.00s
-	//    1    1    1   2,048K     2.20s      2.10s
-
-	// WDTOE: Watchdog Turn-off Enable This bit must
-	// be set when the WDE bit is written to logic zero.
-	// Otherwise, the Watchdog will not be disabled.
-	// Once written to one, hardware will clear this
-	// bit after four clock cycles.
+	// WDCE: Watchdog Change Enable
+	// This bit is used in timed sequences for changing
+	// WDE and prescaler bits. To clear the WDE bit,
+	// and/or change the prescaler bits, WDCE must be
+	// set. Once written to one, hardware will clear
+	// WDCE after four clock cycles.
 
 	// 00001111: Watchdog enabled, 2sec timeout
-	WDTCR = BIT(WDE) | BIT(WDP2) | BIT(WDP1) | BIT(WDP0);
+	WDTCSR = BIT(WDE) | BIT(WDP2) | BIT(WDP1) | BIT(WDP0);
 }
 
 void WDT_SetTimeoutFlag(byte flag)
 {
+	// Currently only support for a maximum of 2 seconds
+	// timeout because there is no need for more and the
+	// bit location of WDP3 requires conditional logic.
+
+	// The sequence for clearing WDE and changing timeout
+	// configuration is as follows:
+
+	// 1. In the same operation, write a logic one to the
+	// Watchdog change enable bit (WDCE) and WDE. A logic
+	// one must be written to WDE regardless of the
+	// previous value of the WDE bit.
+
+	// 2. Within the next four clock cycles, write the WDE
+	// and Watchdog prescaler bits (WDP) as desired, but
+	// with the WDCE bit cleared. This must be done in one
+	// operation.
+
 	flag = CLAMP(flag, 7, 0);
 
 	Info("Setting watchdog prescalar to %02X...", flag);
 
-	// Clear timer prescalar flags
-	WDTCR &= 0xF8; // 11111000
-
-	WDTCR |= flag;
+	// Disable interrupts
+	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
+		WDTCSR = BIT(WDCE) | BIT(WDE);
+		// Set new timer prescalar flag
+		WDTCSR = (WDTCSR & 0xC8) | flag; // C8=11001000
+	}
 }
 
+// XXX: COMMENTS UPDATED!
 bool WDT_HasTriggered(void)
 {
 	bool isreset;
 
 	// To make use of the Reset Flags to identify a reset
 	// condition, the user should read and then reset the
-	// MCUCSR as early as possible in the program. If the
+	// MCUSR as early as possible in the program. If the
 	// register is cleared before another reset occurs,
 	// the source of the reset can be found by examining
 	// the Reset Flags.
 
-	// MCUCSR: MCU Control and Status Register
-	// The MCU Control and Status Register provides
-	// information on which reset source caused an MCU
-	// Reset.
+	// MCUSR: MCU Status Register
+	// The MCU Status Register provides information on
+	// which reset source caused an MCU reset.
 
 	// 7    6    5    4     3     2     1     0
-	// JTD  ISC2   –    JTRF  WDRF  BORF  EXTRF PORF 
+	// -    -    –    JTRF  WDRF  BORF  EXTRF PORF
 
 	// Is watchdog reset flag set?
-	isreset = ((MCUCSR & BIT(WDRF)) != 0);
+	isreset = ((MCUSR & BIT(WDRF)) != 0);
 
 	// XXX: Reset flag detection should be a separate
 	// module to handle the different types.
 
-	MCUCSR = 0;
+	MCUSR = 0;
 
 	return isreset;
 }
 
 void WDT_Disable(void)
 {
-	// WDE can only be cleared if the WDTOE bit has
-	// logic level one. To disable an enabled watchdog
-	// timer, the following procedure must be followed:
+	// See WDT_SetTimeoutFlag for an explanation of the
+	// necessary sequence for clearing WDE and changing
+	// timeout configuration.
 
-	// 1. In the same operation, write a logic one to
-	// WDTOE and WDE. A logic one must be written to WDE
-	// even though it is set to one before the disable
-	// operation starts.
-
-	// 2. Within the next four clock cycles, write a
-	// logic 0 to WDE. This disables the watchdog.
-
-	// No interrupts while we set WDTCR;
+	// Disable interrupts
 	ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
-		WDTCR = BIT(WDTOE) | BIT(WDE);
-		WDTCR = 0;
+		WDTCSR = BIT(WDCE) | BIT(WDE);
+		WDTCSR = 0;
 	}
 }
 

src/common/watchdog.h

@@ -8,7 +8,7 @@
 #define WDT1000  0x6  // 1000 ms
 #define WDT500   0x5  //  500 ms
 #define WDT250   0x4  //  250 ms
-#define WDT100   0x3  //  100 ms
+#define WDT125   0x3  //  125 ms
 #define WDT64    0x2  //   64 ms
 #define WDT32    0x1  //   32 ms
 #define WDT16    0x0  //   16 ms