stm32F4系列MCU，窗口看门狗 WWDG中的bug

stm32F4系列MCU，窗口看门狗 WWDG中的bug。

1. 假如使能预喂狗中止，那么有必要分量如下两点
（1）在舱位wwdg中止之前，需求先将 SR 寄存器中的EWI标志位清零，不然会看门狗会不断复位
（2）在wwdg_irq里加上一小段延时，不然看门狗会不断复位
2. 假如体系里还有其他中止，比方按键，在按键中止中设置一个变量，这个变量在wwdg_isr中读取，来决议是否中止喂狗
这样按下按键今后，体系直接就飞了。
这儿给出一个测验代码。 如下所示。

/* @file    USART/USART_Printf/main.c * @author  MCD Application Team* @version V1.0.1* @date    13-April-2012* @brief   Main program body* @attention** 
 COPYRIGHT 2012 STMicroelectronics
** Licensed under MCD-ST Liberty SW License Agreement V2, (the "License");* You may not use this file except in compliance with the License.* You may obtain a copy of the License at:**        http://www.st.com/software_license_agreement_liberty_v2** Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.* See the License for the specific language governing permissions and* limitations under the License.**//* Includes ------------------------------------------------------------------*/#include "stm32f4xx.h"#include "stm324xg_eval.h"#include / @addtogroup STM32F4xx_StdPeriph_Examples* @{*// @addtogroup USART_Printf* @{*/ /* Private typedef -----------------------------------------------------------*//* Private define ------------------------------------------------------------*//* Private macro -------------------------------------------------------------*//* Private variables ---------------------------------------------------------*/USART_InitTypeDef USART_InitStructure;/* Private function prototypes -----------------------------------------------*/#ifdef __GNUC__/* With GCC/RAISONANCE, small printf (option LD Linker->Libraries->Small printfset to Yes) calls __io_putchar() */#define PUTCHAR_PROTOTYPE int __io_putchar(int ch)#else#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f)#endif /* __GNUC__ *//* Private functions ---------------------------------------------------------*/void delay(int t);void wwdg_nvic_config(void);void key_init(void);/* @brief  Main program* @param  None* @retval None*/int main(void){int i = 0;RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);/*!< At this stage the microcontroller clock setting is already configured, this is done through SystemInit() function which is called from startupfile (startup_stm32f4xx.s) before to branch to application main.To reconfigure the default setting of SystemInit() function, refer tosystem_stm32f4xx.c file*/     /* USARTx configured as follow:- BaudRate = 115200 baud  - Word Length = 8 Bits- One Stop Bit- No parity- Hardware flow control disabled (RTS and CTS signals)- Receive and transmit enabled*/USART_InitStructure.USART_BaudRate = 115200;USART_InitStructure.USART_WordLength = USART_WordLength_8b;USART_InitStructure.USART_StopBits = USART_StopBits_1;USART_InitStructure.USART_Parity = USART_Parity_No;USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;STM_EVAL_COMInit(COM1, &USART_InitStructure);/* Output a message on Hyperterminal using printf function */printf("\n\rUSART Printf Example\n\r");/* key configuration */key_init();/* WWDG configuration *//* Enable WWDG clock */RCC_APB1PeriphClockCmd(RCC_APB1Periph_WWDG, ENABLE);/* WWDG clock counter = (PCLK1 (42MHz)/4096)/8 = 1281 Hz (~780 us)  */WWDG_SetPrescaler(WWDG_Prescaler_8);/* Set Window value to 80; WWDG counter should be refreshed only when the counteris below 80 (and greater than 64) otherwise a reset will be generated */WWDG_SetWindowValue(120);/* Enable WWDG and set counter value to 127, WWDG timeout = ~780 us * 64 = 49.92 ms In this case the refresh window is: ~780 * (127-80) = 36.6ms < refresh window < ~780 * 64 = 49.9ms*/WWDG_Enable(127);wwdg_nvic_config();WWDG->SR = 0;WWDG_EnableIT();  while (1){printf("%d\r\n", i++);delay(1000);}}void delay(int t){int i,j;for(i=0; iSR = 0;if (wwdg_clear_flag == 0) //wwdg_clear_flag 在按键中止中被设置为1{/* Update WWDG counter */WWDG->CR = 127 & 0x7F;delay(1);}}void wwdg_nvic_config(void) {NVIC_InitTypeDef NVIC_InitStructure;NVIC_InitStructure.NVIC_IRQChannel = WWDG_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure);	}static void key_gpio_init(void){GPIO_InitTypeDef GPIO_InitStructure;/* 使能时钟 */RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA | \RCC_AHB1Periph_GPIOF | \RCC_AHB1Periph_GPIOD, ENABLE);GPIO_InitStructure.GPIO_Mode  = GPIO_Mode_IN;GPIO_InitStructure.GPIO_Speed = GPIO_Speed_2MHz;GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;GPIO_InitStructure.GPIO_PuPd  = GPIO_PuPd_DOWN;/* 初始化中止按键 */GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_0;GPIO_Init(GPIOA, &GPIO_InitStructure);/* 初始化轮询按键 */GPIO_InitStructure.GPIO_Pin   = GPIO_Pin_6 | GPIO_Pin_7 | GPIO_Pin_8| GPIO_Pin_9 | GPIO_Pin_10 | GPIO_Pin_11;GPIO_Init(GPIOF, &GPIO_InitStructure);/* 初始化LED引脚 */GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;GPIO_Init(GPIOD, &GPIO_InitStructure);}static void key_exti_config(void){EXTI_InitTypeDef   EXTI_InitStructure;/* 衔接PA0到外部中止线0 */SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOA, EXTI_PinSource0);/* 装备外部中止线0 */EXTI_InitStructure.EXTI_Line = EXTI_Line0;EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising_Falling;EXTI_InitStructure.EXTI_LineCmd = ENABLE;EXTI_Init(&EXTI_InitStructure);}static void key_nvic_config(void){NVIC_InitTypeDef NVIC_InitStructure;/* 使能外部中止0 */NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x3;NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x3;NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;NVIC_Init(&NVIC_InitStructure);}void key_init(void){key_gpio_init();key_exti_config();key_nvic_config();}void EXTI0_IRQHandler(void){ extern int stop_feed_dog;/* 铲除中止标志 */printf("key isr\r\n");wwdg_clear_flag = 1;EXTI_ClearITPendingBit(EXTI_Line0);}/* @}*/ / (C) COPYRIGHT STMicroelectronics *END OF FILE/