WDT (Watchdog Timer)

General Description

High level interface to the Watchdog Timer (WDT).

The WDT can be used for recovering from a CPU or firmware failure. The WDT is initialized with a timeout interval. Once the WDT is started, cyhal_wdt_kick must be called at least once within each timeout interval to reset the count. In case the firmware fails to do so, it is considered to be a CPU crash or firmware failure and the device will be reset.

Features

WDT resets the device if the WDT is not "kicked" using cyhal_wdt_kick within the configured timeout interval.

Quick Start

cyhal_wdt_init() is used to initialize the WDT by providing the WDT object (obj) and the timeout (timeout_ms) value in milliseconds. The timeout parameter can have a minimum value of 1ms. The maximum value of the timeout parameter can be obtained using the cyhal_wdt_get_max_timeout_ms().

Code Snippet

Snippet 1: Initialize the WDT and kick periodically

The following snippet initializes the WDT and illustrates how to reset the WDT within the timeout interval.

    #define LED_ON      0u
    #define LED_OFF     1u
 
    cyhal_wdt_t wdt_obj;
    uint32_t    timeout_ms = 2000; // Minimum value of timeout_ms is 1ms
 
    // Initializing WDT
    rslt = cyhal_wdt_init(&wdt_obj, timeout_ms);
    CY_ASSERT(CY_RSLT_SUCCESS == rslt);
 
    // Initialize the pin connected to an LED on the board
    cyhal_gpio_init(CYBSP_USER_LED, CYHAL_GPIO_DIR_OUTPUT, CYHAL_GPIO_DRIVE_STRONG,
                    CYBSP_LED_STATE_OFF);
 
    // Device power-on reset or XRES event - blink LED once
    cyhal_gpio_write(CYBSP_USER_LED, CYBSP_LED_STATE_ON);
    cyhal_system_delay_ms(100);
    cyhal_gpio_write(CYBSP_USER_LED, CYBSP_LED_STATE_OFF);
    cyhal_system_delay_ms(100);
 
    // Device has restarted due to Watchdog timeout - blink a second time
    if (CYHAL_SYSTEM_RESET_WDT == cyhal_system_get_reset_reason())
    {
        cyhal_gpio_write(CYBSP_USER_LED, CYBSP_LED_STATE_ON);
        cyhal_system_delay_ms(100);
        cyhal_gpio_write(CYBSP_USER_LED, CYBSP_LED_STATE_OFF);
        cyhal_system_delay_ms(100);
    }
 
    // Initialize WDT
    rslt = cyhal_wdt_init(&wdt_obj, timeout_ms);
 
    while (loop)
    {
        // This delay emulates an application task executed between subsequent WDT kicks. Increasing
        // this delay to beyond the programmed WDT timeout will cause a device reset.
        cyhal_system_delay_ms(1000);
 
        // Reset the WDT and avoid a device reset
        cyhal_wdt_kick(&wdt_obj);
    }

API Reference
	WDT HAL Results
	WDT specific return codes.

Functions
cy_rslt_t	cyhal_wdt_init (cyhal_wdt_t *obj, uint32_t timeout_ms)
	Initialize and start the WDT. More...
void	cyhal_wdt_free (cyhal_wdt_t *obj)
	Free the WDT. More...
void	cyhal_wdt_kick (cyhal_wdt_t *obj)
	Resets the WDT. More...
void	cyhal_wdt_start (cyhal_wdt_t *obj)
	Start (enable) the WDT. More...
void	cyhal_wdt_stop (cyhal_wdt_t *obj)
	Stop (disable) the WDT. More...
uint32_t	cyhal_wdt_get_timeout_ms (cyhal_wdt_t *obj)
	Get the WDT timeout. More...
uint32_t	cyhal_wdt_get_max_timeout_ms (void)
	Gets the maximum WDT timeout in milliseconds. More...
bool	cyhal_wdt_is_enabled (cyhal_wdt_t *obj)
	Check if WDT is enabled. More...

Function Documentation

cyhal_wdt_init()

cy_rslt_t cyhal_wdt_init	(	cyhal_wdt_t *	obj,
		uint32_t	timeout_ms
	)

Initialize and start the WDT.

Note

The specified timeout must be at least 1ms and at most the WDT's maximum timeout (see cyhal_wdt_get_max_timeout_ms()).

Parameters

[out]	obj	Pointer to a WDT object. The caller must allocate the memory for this object but the init function will initialize its contents.
[in,out]	timeout_ms	The time in milliseconds before the WDT times out (1ms - max) (see cyhal_wdt_get_max_timeout_ms())

Returns

The status of the init request

Returns CY_RSLT_SUCCESS if the operation was successfull.

cyhal_wdt_free()

void cyhal_wdt_free

(

cyhal_wdt_t *

obj

)

Free the WDT.

Powers down the WDT. Releases object (obj). After calling this function no other WDT functions should be called except cyhal_wdt_init().

Parameters

[in,out]

obj

The WDT object

cyhal_wdt_kick()

void cyhal_wdt_kick

(

cyhal_wdt_t *

obj

)

Resets the WDT.

This function must be called periodically to prevent the WDT from timing out and resetting the device.

See Snippet 1: Initialize the WDT and kick periodically

Parameters

[in,out]

obj

The WDT object

cyhal_wdt_start()

void cyhal_wdt_start

(

cyhal_wdt_t *

obj

)

Start (enable) the WDT.

Parameters

[in,out]

obj

The WDT object

cyhal_wdt_stop()

void cyhal_wdt_stop

(

cyhal_wdt_t *

obj

)

Stop (disable) the WDT.

Parameters

[in,out]

obj

The WDT object

cyhal_wdt_get_timeout_ms()

uint32_t cyhal_wdt_get_timeout_ms

(

cyhal_wdt_t *

obj

)

Get the WDT timeout.

Gets the configured time, in milliseconds, before the WDT times out.

Parameters

[in]

obj

The WDT object

Returns

The time in milliseconds before the WDT times out

cyhal_wdt_get_max_timeout_ms()

uint32_t cyhal_wdt_get_max_timeout_ms

(

void

)

Gets the maximum WDT timeout in milliseconds.

Returns

The maximum timeout for the WDT

cyhal_wdt_is_enabled()

bool cyhal_wdt_is_enabled

(

cyhal_wdt_t *

obj

)

Check if WDT is enabled.

This will return true after cyhal_wdt_start is called. It will return false before the WDT is started, or after cyhal_wdt_stop is called.

Parameters

[in]

obj

The WDT object

Returns

The status of WDT is_enabled request