Watchdogs
[Device Driver API.]

Collaboration diagram for Watchdogs:

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Detailed Description

Watchdog Support.

Platform independent watchdog support is available for the AVR platform and the AT91R40008 MCU.

Functions
u_long	NutWatchDogStart (u_long ms, u_long xmode)
	Start the watch dog timer.
void	NutWatchDogRestart (void)
	Restart the watch dog timer.
void	NutWatchDogDisable (void)
	Disables the watch dog timer.
void	NutWatchDogEnable (void)
	Enables the watch dog timer.

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Function Documentation

u_long NutWatchDogStart (  u_long  ms, u_long  xmode )

Start the watch dog timer. This function can be used by applications to prevent hang-ups. Parameters: ms  Watch dog time out in milliseconds. xmode  Hardware specific mode. If 0, the default mode is used. In this mode, the watch dog will reset the CPU if not restarted within the specified time out period. Returns: The actual time out value, which may differ from the specified value due to hardware limitations. The watch dog timer will be automatically enabled on return. The following code fragment starts the watch timer with a time out of 550 milliseconds and restarts it every 500 milliseconds. #include <dev/watchdog.h> #include <sys/timer.h> NutWatchDogStart(550, 0); for(;;) { NutWatchDogRestart(); NutSleep(500); } Todo: AVR implementation. Note: The AT91 implementation does not calculate the actual time out value, but simply returns the specified number of milliseconds.

void NutWatchDogDisable (  void   )

Disables the watch dog timer. Applications should call this function to temporarily disable the watch dog timer. To re-enable it, call NutWatchDogEnable(). #include <dev/watchdog.h> NutWatchDogStart(100, 0); //Some code here. NutWatchDogRestart(); //Some code here. NutWatchDogDisable(); //Some lengthy code here, like writing to flash memory. NutWatchDogEnable();

void NutWatchDogEnable (  void   )

Enables the watch dog timer. The function can be safely used within nested subroutines. The watch dog will be enabled only, if this function is called the same number of times as NutWatchDogDisable(). If enabled, the watch dog timer will also have been re-started and the full time out value is available before another NutWatchDogRestart() is required. If the watch has not been started by NutWatchDogStart(), then this function does nothing.

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