WDT Interface

Driver API for WDT (plib_wdt.h) More...

Typedefs
typedef void(*	WDT_CALLBACK_HANDLER) (void)
	Function pointer type for Watchdog Timer callback.
typedef uint8_t	WDT_TIMEOUT_PERIOD
	WDT timeout period identifier.
typedef uint8_t	WDT_WINDOW_CLOSED_PERIOD
	WDT window closed period identifier.
typedef uint8_t	WDT_EARLY_WARNING_OFFSET
	WDT early warning offset identifier.

Functions
void	WDT_Enable (void)
	Enables the Watchdog Timer.
void	WDT_Disable (void)
	Disables the Watchdog Timer.
void	WDT_Clear (void)
	Clears (refreshes) the Watchdog Timer.
void	WDT_SetCallbackHandler (WDT_CALLBACK_HANDLER callback)
	Registers the callback handler to be invoked from the WDT ISR.
void	WDT_SetTimeout (WDT_TIMEOUT_PERIOD period)
	Sets the WDT timeout period.
bool	WDT_EnableWindowMode (WDT_WINDOW_CLOSED_PERIOD window)
	Enables the WDT window mode.
void	WDT_DisableWindowMode (void)
	Disables the WDT window mode.
bool	WDT_SetEarlyWarningOffset (WDT_EARLY_WARNING_OFFSET offset)
	Sets the WDT early warning offset.
bool	WDT_IsAlwaysOn (void)
	Checks if the WDT is configured as always-on.
void	WDT_EnableEarlyWarning (void)
	Enables WDT Early Warning interrupt.
void	WDT_DisableEarlyWarning (void)
	Disables WDT Early Warning interrupt.
bool	WDT_EarlyWarningIsSet (void)
	Checks if Early Warning interrupt flag is set.
void	WDT_ClearEarlyWarning (void)
	Clears Early Warning interrupt flag.

Description

Driver API for WDT (plib_wdt.h)

Usage Example

The following example demonstrates typical usage of the WDT peripheral:

 
#include "plib_wdt.h"
#include <pic32c.h>
#include <stdint.h>
 
 
/*******************************************************************************
 * @brief Configure WDT in Normal Mode
 *
 * In Normal Mode:
 * - The watchdog counts continuously.
 * - The application must periodically call WDT_Clear().
 * - An Early Warning interrupt can occur before the timeout.
 *
 * WDT CLK timing (1.024 kHz clock):
 *   Timeout period = 4096 cycles ≈ 4 seconds
 *   Early warning offset = 512 cycles ≈ 0.5 s after start
 *
 * Timeline:
 *
 *  WDT_Clear()
 *      ↓0                   0.5                         4
 *      |------ offset ------|-------- remaining --------|
 *      ↑                    ↑                           ↑
 *    start            Early Warning                 Reset
 ******************************************************************************/
int32_t configure_wdt_normal_mode(void (*callback)(void))
{
    // Configure watchdog timeout period 
    WDT_SetTimeout(WDT_CONFIG_PER_CYC4096_Val);
 
    // Configure Early Warning offset 
    WDT_SetEarlyWarningOffset(WDT_EWCTRL_EWOFFSET_CYC512_Val);
 
    // Enable Early Warning interrupt 
    WDT_EnableEarlyWarning();
 
    // Register callback handler if provided 
    if (callback != NULL)
    {
        WDT_SetCallbackHandler(callback);
    }
 
    // Enable WDT interrupt at CPU level 
    NVIC_EnableIRQ(WDT_IRQn);
 
    // Start the watchdog timer 
    WDT_Enable();
 
    return 0;
}
 
 
/*******************************************************************************
 * @brief Configure WDT in Window Mode
 *
 * In Window Mode:
 * - The watchdog can only be cleared during the open window.
 * - Clearing the watchdog too early or too late triggers a reset.
 *
 * WDT CLK timing (1.024 kHz clock):
 *
 *   Timeout = 4096 cycles ≈ 4 seconds
 *   Closed window = 1024 cycles ≈ 1 second
 *
 * Timeline:
 *
 *  WDT_Enable() / WDT_Clear()
 *      ↓0               1                            5
 *      |---- CLOSED ----|----------- OPEN -----------|
 *      ↑                ↑                           ↑
 *    start          window opens                 Reset
 *
 ******************************************************************************/
int32_t configure_wdt_window_mode(void (*callback)(void))
{
    // Configure watchdog timeout period 
    WDT_SetTimeout(WDT_CONFIG_PER_CYC4096_Val);
 
    // Enable window mode with closed window period 
    WDT_EnableWindowMode(WDT_CONFIG_WINDOW_CYC1024_Val);
 
    // Enable Early Warning interrupt 
    WDT_EnableEarlyWarning();
 
    // Register callback handler 
    if (callback != NULL)
    {
        WDT_SetCallbackHandler(callback);
    }
 
    // Enable WDT interrupt in NVIC 
    NVIC_EnableIRQ(WDT_IRQn);
 
    // Start watchdog timer 
    WDT_Enable();
 
    return 0;
}

Typedef Documentation

WDT_CALLBACK_HANDLER

typedef void(* WDT_CALLBACK_HANDLER) (void)

Function pointer type for Watchdog Timer callback.

WDT_EARLY_WARNING_OFFSET

WDT_EARLY_WARNING_OFFSET

WDT early warning offset identifier.

Defines how many watchdog clock cycles before timeout the Early Warning interrupt is generated.

WDT_TIMEOUT_PERIOD

WDT_TIMEOUT_PERIOD

WDT timeout period identifier.

A system reset occurs if the watchdog is not cleared before timeout.

WDT_WINDOW_CLOSED_PERIOD

WDT_WINDOW_CLOSED_PERIOD

WDT window closed period identifier.

Defines the time interval during which clearing the watchdog is not allowed when Window Mode is enabled. Writing CLEAR during this closed window causes an immediate reset.

Function Documentation

WDT_Clear()

void WDT_Clear

(

void

)

Clears (refreshes) the Watchdog Timer.

Resets the WDT counter to avoid system reset. Must be called periodically.

Returns

void

WDT_ClearEarlyWarning()

void WDT_ClearEarlyWarning

(

void

)

Clears Early Warning interrupt flag.

Returns

void

WDT_Disable()

void WDT_Disable

(

void

)

Disables the Watchdog Timer.

Stops the WDT from counting down.

Returns

void

WDT_DisableEarlyWarning()

void WDT_DisableEarlyWarning

(

void

)

Disables WDT Early Warning interrupt.

Returns

void

WDT_DisableWindowMode()

void WDT_DisableWindowMode

(

void

)

Disables the WDT window mode.

Disables the restricted window requirement for clearing the WDT.

Returns

void

WDT_EarlyWarningIsSet()

bool WDT_EarlyWarningIsSet

(

void

)

Checks if Early Warning interrupt flag is set.

Returns

true if the early warning flag is set, false otherwise.

WDT_Enable()

void WDT_Enable

(

void

)

Enables the Watchdog Timer.

Starts the WDT countdown.

Returns

void

WDT_EnableEarlyWarning()

void WDT_EnableEarlyWarning

(

void

)

Enables WDT Early Warning interrupt.

Returns

void

WDT_EnableWindowMode()

bool WDT_EnableWindowMode

(

WDT_WINDOW_CLOSED_PERIOD

window

)

Enables the WDT window mode.

When enabled, the WDT must be cleared only within a specific window period.

Parameters

window

Window size to configure.

Returns

true if enabled successfully, false otherwise.

WDT_IsAlwaysOn()

bool WDT_IsAlwaysOn

(

void

)

Checks if the WDT is configured as always-on.

Some devices may not allow disabling the WDT. This function returns that status.

Returns

true if the WDT is always-on, false otherwise.

WDT_SetCallbackHandler()

void WDT_SetCallbackHandler

(

WDT_CALLBACK_HANDLER

callback

)

Registers the callback handler to be invoked from the WDT ISR.

Parameters

callback

Pointer to the callback function.

This function is used to set a user-defined function that will be called when a WDT interrupt or timeout event occurs.

WDT_SetEarlyWarningOffset()

bool WDT_SetEarlyWarningOffset

(

WDT_EARLY_WARNING_OFFSET

offset

)

Sets the WDT early warning offset.

Configures the Early Warning interrupt offset. Valid only in normal mode.

Parameters

offset

Early warning offset value.

Returns

true if set successfully, false otherwise.

WDT_SetTimeout()

void WDT_SetTimeout

(

WDT_TIMEOUT_PERIOD

period

)

Sets the WDT timeout period.

Configures the WDT to timeout after the given period.

Parameters

period

The timeout value in supported units (hardware-dependent).