I use NXP LPC54618 sdk to test wwdog ，I find that the wwdog is not precise ？ When I set wwdog window value is 1s ,but it seems like 800 ms feed dog once?
my code :
void delayWwdtWindow(void)
{
/* For the TV counter register value will decrease after feed watch dog,
* we can use it to as delay. But in user scene, user need feed watch dog
* in the time period after enter Window but before warning intterupt.
*/
while (WWDT->TV > WWDT->WINDOW)
{
__NOP();
}
}
/*!
* @brief Main function
*/
int main(void)
{
wwdt_config_t config;
uint32_t wdtFreq;
bool timeOutResetEnable;
/* Init hardware*/
CLOCK_EnableClock(kCLOCK_Gpio0);
CLOCK_EnableClock(kCLOCK_Gpio2);
/* attach 12 MHz clock to FLEXCOMM0 (debug console) */
CLOCK_AttachClk(BOARD_DEBUG_UART_CLK_ATTACH);
BOARD_InitPins(); //2_2 LED3
BOARD_BootClockPLL180M();
BOARD_InitDebugConsole();
/* Set Red LED to initially be high */
APP_LED_INIT;
#if !defined(FSL_FEATURE_WWDT_HAS_NO_PDCFG) || (!FSL_FEATURE_WWDT_HAS_NO_PDCFG)
POWER_DisablePD(kPDRUNCFG_PD_WDT_OSC);
#endif
/* Enable the WWDT time out to reset the CPU. */
timeOutResetEnable = true;
/* Check if reset is due to Watchdog */
if (WWDT_GetStatusFlags(WWDT) & kWWDT_TimeoutFlag)
{
APP_LED_ON;
PRINTF("Watchdog reset occurred\r\n");
timeOutResetEnable = false;
/* The timeout flag can only clear when and after wwdt intial. */
}
/* wdog refresh test in window mode/timeout reset */
PRINTF("\r\n--- %s test start ---\r\n", (timeOutResetEnable) ? "Time out reset" : "Window mode refresh");
/* The WDT divides the input frequency into it by 4 */
wdtFreq = WDT_CLK_FREQ / 4;
WWDT_GetDefaultConfig(&config);
/*
* Set watchdog feed time constant to approximately 4s
* Set watchdog warning time to 512 ticks after feed time constant
* Set watchdog window time to 1s
*/
config.timeoutValue = wdtFreq * 4 ;
config.warningValue = 512;
config.windowValue = wdtFreq * 1;
/* Configure WWDT to reset on timeout */
config.enableWatchdogReset = true;
/* Setup watchdog clock frequency(Hz). */
config.clockFreq_Hz = WDT_CLK_FREQ;
WWDT_Init(WWDT, &config);
// NVIC_EnableIRQ(APP_WDT_IRQn);
while (1)
{
if (timeOutResetEnable)
{
/* SDK_DelayAtLeastUs can be replaced by Detail User code*/
SDK_DelayAtLeastUs(1000, SDK_DEVICE_MAXIMUM_CPU_CLOCK_FREQUENCY);
}
else
{
/* The WINDOW register determines the highest TV value allowed when a watchdog feed is
* performed. If a feed sequence occurs when TV is greater than the value in WINDOW, a
* watchdog event will occur. User can set window same as timeout value if required. */
delayWwdtWindow();
WWDT_Refresh(WWDT);
APP_LED_TOGGLE; //use a oscilloscope to check time if precise
// PRINTF(" WDOG has been refreshed!\r\n");
/* SDK_DelayAtLeastUs can be replaced by Detail User code*/
// SDK_DelayAtLeastUs(1000, SDK_DEVICE_MAXIMUM_CPU_CLOCK_FREQUENCY);
}
}
}
thank you！
