STM32F2系列的EXTI使用說明
1. 外部中斷事件線的映射
140個GPIO連接到了16個外部中斷/事件線，如下圖所示：
GPIO與外部中斷/事件線關聯圖
另外7個外部中斷/事件線分別連接：
EXTI Line 16：PVD輸出；
EXTI Line 17：RTC報警事件；
EXTI Line 18：USB OTG FS喚醒事件；
EXTI Line 19：以太網喚醒事件；
EXTI Line 20：USB OTG HS喚醒事件；
EXTI Line 21：RTC Tamper and TimeStamp事件
EXTI Line 22：RTC喚醒事件。
2. EXTI與SYSCFG(System configurationcontroller)關係
SYSCFG主要用於重新定位存儲器在代碼空間的位置，用於選擇以太網的PHY和管理外部中斷線與GPIO的聯繫。
如下圖所示，用於配置外部中斷並連接到EXTI外部中斷。
3. EXTI初始化
voidKEY_EXTI_Initialize(void)
{
EXTI_InitTypeDef EXTI_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
/* Enable GPIOC clock */
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC,ENABLE);
/* Enable SYSCFG clock */
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG,ENABLE);
/* Configure PC2 pin as input floating */
GPIO_InitStructure.GPIO_Mode= GPIO_Mode_IN;
GPIO_InitStructure.GPIO_PuPd= GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Pin= GPIO_Pin_2;
GPIO_Init(GPIOC,&GPIO_InitStructure);
/* Connect EXTI Line2 to PC2 pin */
SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOC,EXTI_PinSource2);
/* Configure EXTI Line2 */
EXTI_InitStructure.EXTI_Line= EXTI_Line2;
EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
EXTI_InitStructure.EXTI_Trigger= EXTI_Trigger_Falling;
EXTI_InitStructure.EXTI_LineCmd= ENABLE;
EXTI_Init(&EXTI_InitStructure);
/*Enable and set EXTI Line2 Interrupt to the lowest priority */
NVIC_InitStructure.NVIC_IRQChannel =EXTI2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority= 0x0F;
NVIC_InitStructure.NVIC_IRQChannelSubPriority= 0x0F;
NVIC_InitStructure.NVIC_IRQChannelCmd= ENABLE;
NVIC_Init(&NVIC_InitStructure);
}
3.1.使能作爲外部中斷的引腳的GPIO端口時鐘
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC,ENABLE);
3.2.使能SYSCFG時鐘
RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG,ENABLE);
3.3.初始化GPIO引腳
GPIO_InitStructure.GPIO_Mode =GPIO_Mode_IN;
GPIO_InitStructure.GPIO_PuPd= GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Pin= GPIO_Pin_2;
GPIO_Init(GPIOC,&GPIO_InitStructure);
3.4.連接引腳到外部中斷線
SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOC,EXTI_PinSource2);
說明：每個引腳對應相應的線，如GPIO1則對應EXTI_PinSource1，查看1中的圖。
3.5.配置外部中斷線
EXTI_InitStructure.EXTI_Line =EXTI_Line2;
EXTI_InitStructure.EXTI_Mode =EXTI_Mode_Interrupt;
EXTI_InitStructure.EXTI_Trigger= EXTI_Trigger_Falling;
EXTI_InitStructure.EXTI_LineCmd= ENABLE;
EXTI_Init(&EXTI_InitStructure);
3.6.使能中斷
NVIC_InitStructure.NVIC_IRQChannel= EXTI2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority= 0x0F;
NVIC_InitStructure.NVIC_IRQChannelSubPriority= 0x0F;
NVIC_InitStructure.NVIC_IRQChannelCmd= ENABLE;
NVIC_Init(&NVIC_InitStructure);
記得對IRQChannelPreemptionPriority和IRQChannelSubPriority賦值均爲0x0F。
4. EXTI中斷函數
voidEXTI2_IRQHandler(void)
{
if(EXTI_GetITStatus(EXTI_Line2) != RESET)
{
/* LED1閃爍標識符 */
LED1_flag = 1;
/* LED1閃爍次數 */
LED1_Twinkle_Num = 2*Twinkle_Num;
g_OD.Position_Offset =g_OD.current_angle;
/* Clear the EXTI line 0 pending bit */
EXTI_ClearITPendingBit(EXTI_Line2);
}
}