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在STM32开发中经常会用到独立看门狗（IWDG）和低功耗模式，看门狗是为了检测和解决由软件错误引起的故障，低功耗模式是为了在CPU不需要继续运行时进入到休眠模式用以节省电能。其中独立看门狗的时钟由独立的RC振荡器（STM32F10x一般为40kHz）提供，即使在主时钟出现故障时，也仍然有效，因此可以在停止和待机模式下工作。而且独立看门狗一旦启动，除了系统复位，它不能再被停止。但这样引发的一个问题是当MCU进入到低功耗模式后由于CPU停止运行无法喂狗，会导致系统频繁复位。那如何解决这个问题呢，难道独立看门狗和低功耗模式没法同时使用？
一个很好的方式是在休眠模式下通过RTC定时唤醒来喂狗，喂完够在进入继续进入到休眠模式。比如看门狗复位的时间间隔为10s。那么在进入休眠模式前设置RTC闹钟中断时间为5s。这样每隔5s唤醒一次喂一次狗。便可以很好的解决这个问题。
while(1)
{
// 执行任务
Task1();
Task2();
// ..
// 喂狗
dev_iwdg_feed();
// 进入待机模式开关
if(m_bEnterStandByMode)
{
// 使能外部中断，GPIOB3，用以MCU从待机模式唤醒
dev_exti_enable(TRUE);
ENTERSTOPMODE:
// 设置RTC闹钟，5秒钟产生一次RTC闹钟中断*/
dev_rtc_setAlarm(5);
// 进入停止模式（低功耗），直至外部中断触发时被唤醒
PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);
// 是否是RTC闹钟中断唤醒
if(dev_rtc_isAlarm())
{
// 喂狗
dev_iwdg_feed();
// 喂完狗继续进入停止模式
goto ENTERSTOPMODE;
}
// 禁止外部中断
dev_exti_enable(FALSE);
// 从停止模式唤醒后恢复系统时钟
dev_clk_restore();
}
}
以下是完整的参考代码：
//**********************************************************************************************
// STM32F10x StopMode RTC Feed Dog
// compiler: Keil UV3
// 2013-01-04 , By friehood
//**********************************************************************************************
#include "stm32f10x_lib.h"
#include "platform_config.h"
static Boolean g_bRTCAlarm = FALSE;
/*******************************************************************************
* Function Name : RCC_Configuration
* Description : Configures the different system clocks.
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void RCC_Configuration(void)
{
/* RCC system reset(for debug purpose) */
RCC_DeInit();
/* Enable HSE */
RCC_HSEConfig(RCC_HSE_ON);
/* Wait till HSE is ready */
if(RCC_WaitForHSEStartUp() == SUCCESS)
{
/* Enable Prefetch Buffer */
FLASH_PrefetchBufferCmd(FLASH_PrefetchBuffer_Enable);
//FLASH时序控制
//推荐值：SYSCLK = 0~24MHz Latency=0
// SYSCLK = 24~48MHz Latency=1
// SYSCLK = 48~72MHz Latency=2
//FLASH_SetLatency(FLASH_Latency_1); //警告:修改为1会对DMA值有影响（如ADC采集值会错位）
FLASH_SetLatency(FLASH_Latency_2);
/* HCLK = SYSCLK */
RCC_HCLKConfig(RCC_SYSCLK_Div1);
/* PCLK2 = HCLK */
RCC_PCLK2Config(RCC_HCLK_Div1);
/* PCLK1 = HCLK/2 */
RCC_PCLK1Config(RCC_HCLK_Div2);
/* PLLCLK = 12MHz * 3 = 36 MHz */
RCC_PLLConfig(RCC_PLLSource_HSE_Div1, RCC_PLLMul_3);
/* Enable PLL */
RCC_PLLCmd(ENABLE);
/* Wait till PLL is ready */
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
{
}
/* Select PLL as system clock source */
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
/* Wait till PLL is used as system clock source */
while(RCC_GetSYSCLKSource() != 0x08)
{
}
}
/* Enable PWR and BKP clock */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE);
/* Enable AFIO clock */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
}
/*******************************************************************************
* Function Name : NVIC_Configuration
* Description : Configures the nested vectored interrupt controller.
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void NVIC_Configuration(void)
{
NVIC_InitTypeDef NVIC_InitStructure;
#ifdef VECT_TAB_RAM
/* Set the Vector Table base location at 0x20000000 */
NVIC_SetVectorTable(NVIC_VectTab_RAM, 0x0);
#else /* VECT_TAB_FLASH */
/* Set the Vector Table base location at 0x08000000 */
NVIC_SetVectorTable(NVIC_VectTab_FLASH, 0x0);
#endif
/* Configure one bit for preemption priority */
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);
}
/*******************************************************************************
* Function Name : SysTick_Configuration
* Description : Configures the SysTick to generate an interrupt each 1 millisecond.
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void SysTick_Configuration(void)
{
/* Select AHB clock(HCLK) as SysTick clock source */
SysTick_CLKSourceConfig(SysTick_CLKSource_HCLK);
/* Set SysTick Priority to 3 */
NVIC_SystemHandlerPriorityConfig(SystemHandler_SysTick, 3, 0);
/* SysTick interrupt each 1ms with HCLK equal to 72MHz */
SysTick_SetReload(72000);
/* Enable the SysTick Interrupt */
SysTick_ITConfig(ENABLE);
}
/*******************************************************************************
* Function Name : Delay
* Description : Inserts a delay time.
* Input : nTime: specifies the delay time length, in milliseconds.
* Output : None
* Return : None
*******************************************************************************/
void Delay(u32 nTime)
{
/* Enable the SysTick Counter */
SysTick_CounterCmd(SysTick_Counter_Enable);
TimingDelay = nTime;
while(TimingDelay != 0);
/* Disable the SysTick Counter */
SysTick_CounterCmd(SysTick_Counter_Disable);
/* Clear the SysTick Counter */
SysTick_CounterCmd(SysTick_Counter_Clear);
}
/*******************************************************************************
* Function Name : RTC_Configuration
* Description : Configures RTC clock source and prescaler.
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void RTC_Configuration(void)
{
EXTI_InitTypeDef EXTI_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
/* RTC clock source configuration ------------------------------------------*/
/* Allow access to BKP Domain */
PWR_BackupAccessCmd(ENABLE);
/* Reset Backup Domain */
BKP_DeInit();
/* Enable the LSI OSC */
RCC_LSICmd(ENABLE);
/* Wait till LSI is ready */
while (RCC_GetFlagStatus(RCC_FLAG_LSIRDY) == RESET){}
/* Select the RTC Clock Source */
RCC_RTCCLKConfig(RCC_RTCCLKSource_LSI);
/* Enable the RTC Clock */
RCC_RTCCLKCmd(ENABLE);
/* RTC configuration -------------------------------------------------------*/
/* Wait for RTC APB registers synchronisation */
RTC_WaitForSynchro();
/* Set RTC prescaler: set RTC period to 1sec */
RTC_SetPrescaler(40000);
/* Wait until last write operation on RTC registers has finished */
RTC_WaitForLastTask();
/* Enable the RTC Alarm interrupt */
RTC_ITConfig(RTC_IT_ALR, ENABLE);
/* Wait until last write operation on RTC registers has finished */
RTC_WaitForLastTask();
/* Configure EXTI Line17(RTC Alarm) to generate an interrupt on rising edge */
EXTI_ClearITPendingBit(EXTI_Line17);
EXTI_InitStructure.EXTI_Line = EXTI_Line17;
EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
EXTI_InitStructure.EXTI_LineCmd = ENABLE;
EXTI_Init(&EXTI_InitStructure);
/* Enable the RTC Interrupt */
NVIC_InitStructure.NVIC_IRQChannel = RTCAlarm_IRQChannel;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
}
/*******************************************************************************
* Function Name : RTCAlarm_IRQHandler
* Description : This function handles RTC Alarm interrupt request.
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void RTCAlarm_IRQHandler(void)
{
if(RTC_GetITStatus(RTC_IT_ALR) != RESET)
{
/* Set the RTC alarm flag */
g_bRTCAlarm = TRUE;
/* Clear EXTI line17 pending bit */
EXTI_ClearITPendingBit(EXTI_Line17);
/* Check if the Wake-Up flag is set */
if(PWR_GetFlagStatus(PWR_FLAG_WU) != RESET)
{
/* Clear Wake Up flag */
PWR_ClearFlag(PWR_FLAG_WU);
}
/* Wait until last write operation on RTC registers has finished */
RTC_WaitForLastTask();
/* Clear RTC Alarm interrupt pending bit */
RTC_ClearITPendingBit(RTC_IT_ALR);
/* Wait until last write operation on RTC registers has finished */
RTC_WaitForLastTask();
}
}
/*******************************************************************************
* Function Name : dev_rtc_setAlarm
* Description : 设置RTC闹钟.
* Input : 闹钟时间
* Output : None
* Return : None
*******************************************************************************/
void dev_rtc_setAlarm(u32 AlarmValue)
{
/* Clear the RTC SEC flag */
RTC_ClearFlag(RTC_FLAG_SEC);
/* Wait clear RTC flag sccess */
while(RTC_GetFlagStatus(RTC_FLAG_SEC) == RESET);
/* Wait until last write operation on RTC registers has finished */
RTC_WaitForLastTask();
/* Sets the RTC alarm value */
RTC_SetAlarm(RTC_GetCounter() + AlarmValue);
/* Wait until last write operation on RTC registers has finished */
RTC_WaitForLastTask();
}
/*******************************************************************************
* Function Name : dev_rtc_isAlarm
* Description : RTC闹钟是否触发
* Input : None
* Output : None
* Return : TRUE:已触发，FALSE，未触发
*******************************************************************************/
Boolean dev_rtc_isAlarm(void)
{
if(g_bRTCAlarm)
{
/* Clear the RTC alarm flag */
g_bRTCAlarm = FALSE;
return TRUE;
}
return FALSE;
}
void dev_iwdg_init(void)
{
/* Enable write access to IWDG_PR and IWDG_RLR registers */
IWDG_WriteAccessCmd(IWDG_WriteAccess_Enable);
/* IWDG counter clock: 40KHz(LSI) / 256 = 0.15625 KHz */
IWDG_SetPrescaler(IWDG_Prescaler_256);
/* Set counter reload value to 1562 */
IWDG_SetReload(1562); // 10s
/* Reload IWDG counter */
IWDG_ReloadCounter();
/* Enable IWDG (the LSI oscillator will be enabled by hardware) */
IWDG_Enable();
}
void dev_iwdg_feed(void)
{
IWDG_ReloadCounter();
}
/*******************************************************************************
* Function Name : dev_clk_restore
* Description : Restore system clock after wake-up from STOP: enable HSE, PLL
* and select PLL as system clock source.
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void dev_clk_restore(void)
{
/* Enable HSE */
RCC_HSEConfig(RCC_HSE_ON);
/* Wait till HSE is ready */
HSEStartUpStatus = RCC_WaitForHSEStartUp();
if(HSEStartUpStatus == SUCCESS)
{
/* Enable PLL */
RCC_PLLCmd(ENABLE);
/* Wait till PLL is ready */
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET)
{
}
/* Select PLL as system clock source */
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);
/* Wait till PLL is used as system clock source */
while(RCC_GetSYSCLKSource() != 0x08)
{
}
}
}
/*******************************************************************************
* Function Name : EXTI_Configuration
* Description : Configures EXTI Line3.
* Input : None
* Output : None
* Return : None
*******************************************************************************/
void EXIT_Configuration(void)
{
EXTI_InitTypeDef EXTI_InitStructure;
GPIO_EXTILineConfig(GPIO_PortSourceGPIOB,GPIO_PinSource3);
EXTI_ClearITPendingBit(EXTI_Line3);
EXTI_InitStructure.EXTI_Line = EXTI_Line3;
EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling;
EXTI_InitStructure.EXTI_LineCmd = ENABLE;
EXTI_Init(&EXTI_InitStructure);
}
void dev_exti_enable(Boolean bEnable)
{
NVIC_InitTypeDef NVIC_InitStructure;
/* Clear the Key Button EXTI line pending bit */
EXTI_ClearITPendingBit(EXTI_Line3);
NVIC_ClearIRQChannelPendingBit(EXTI3_IRQChannel);
NVIC_InitStructure.NVIC_IRQChannel = EXTI3_IRQChannel;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = bEnable ? ENABLE : DISABLE;
NVIC_Init(&NVIC_InitStructure);
}
/*******************************************************************************
* Function Name : main
* Description : Main program.
* Input : None
* Output : None
* Return : None
*******************************************************************************/
int main(void)
{
/* System Clocks Configuration */
RCC_Configuration();
/* NVIC configuration */
NVIC_Configuration();
/* Configure RTC clock source and prescaler */
RTC_Configuration();
/* Configure the SysTick to generate an interrupt each 1 millisecond */
SysTick_Configuration();
/* Configures EXTI Line3 */
EXIT_Configuration();
/* IWDG initialize*/
dev_iwdg_init();
while(1)
{
// 执行任务
Task1();
Task2();
// ..
// 喂狗
dev_iwdg_feed();
// 进入待机模式开关
if(m_bEnterStandByMode)
{
// 使能外部中断，GPIOB3，用以MCU从待机模式唤醒
dev_exti_enable(TRUE);
ENTERSTOPMODE:
// 设置RTC闹钟，5秒钟产生一次RTC闹钟中断*/
dev_rtc_setAlarm(5);
// 进入停止模式（低功耗），直至外部中断触发时被唤醒
PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);
// 是否是RTC闹钟中断唤醒
if(dev_rtc_isAlarm())
{
// 喂狗
dev_iwdg_feed();
// 喂完狗继续进入停止模式
goto ENTERSTOPMODE;
}
// 禁止外部中断
dev_exti_enable(FALSE);
// 从停止模式唤醒后恢复系统时钟
dev_clk_restore();
}
}
}
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