灵动微课堂 (第202讲) | MM32F0140 EXTI 学习笔记

// Clear EXTI2 and assign value, the corresponding value of PB is 0001.
SYSCFG->EXTICR1 = ( ( SYSCFG->EXTICR1 & ~(0xf << 8u) ) | (0x1 << 8u) );配置触发类型在按键初始化中配置按键未按下时处于高电平，因此，对上升沿触发选择寄存器（EXTI_RTSR）与下降沿触发选择寄存器（EXTI_FTSR）赋值时配置触发类型为下降沿触发。// Clear the corresponding bit of EXTI2 triggered by rising edge.
EXTI->RTSR &= ~ (1u << 2u);
// Configure falling edge trigger.
EXTI->FTSR |= (1u << 2u);使能中断配置EXTI_IMR寄存器的EXTI2对应位，使能中断。// Enable EXTI interrupt.
EXTI->IMR |= (1u << 2u);配置NVICEXTI控制中断，NVIC处理中断，使用Cortex-M0 core_cm0.h头文件中的NVIC_EnableIRQ使能中断线，EXTI2对应中断为EXTI2_3_IRQn。// Setup NVIC.
NVIC_EnableIRQ (EXTI2_3_IRQn);编写中断服务程序中断使能中使用EXTI2_3_IRQn，中断处理函数要与其匹配，因此使用EXTI2_3_IRQHandler，设置变量app_exti_event_on作为中断状态标志，该变量初始时为false，中断请求产生时中断状态标志转换为true，将EXRI_PR寄存器的对应位写入1来清除中断。void EXTI2_3_IRQHandler(void)
{
    uint32_t flags = EXTI->PR;
    if ( 0u != ( flags & (1u << 2u) ) )
    {
        app_exti_event_on = true;
    }

    EXTI->PR |= (1u << 2u); // Clear interrupt.
}main()函数主程序中初始化变量app_exti_event_times为0，设置该变量从0开始计数，当中断状态标志app_exti_event_on为true，即产生中断请求时，计数值加1，由于LED2初始化后显示为亮，计算计数值取余2，若余数不等于0则LED2灭，若余数为0则LED2亮。实验效果如图7所示。int main(void)
{
    // Enable SYSCFG and GPIOB clock.
    RCC->APB2ENR |= (1u << 0u);
    RCC->AHB1ENR |= (1u << 18u);

    // Setup K2.
    GPIOB->CRL &= ~(0xf << 8u);
    GPIOB->CRL |= (0x8 << 8u);
    GPIOB->BSRR |= (1u << 2u);

    // Setup LED2.
    GPIOB->CRL &= ~(0xf << 12u);
    GPIOB->CRL |= (0x1 << 12u);

    // Setup SYSCFG EXTI2.
    SYSCFG->EXTICR1 = ( ( SYSCFG->EXTICR1 & ~(0xf << 8u) ) | (0x1 << 8u) );

    // Setup EXTI.
    EXTI->RTSR &= ~ (1u << 2u);
    EXTI->FTSR |= (1u << 2u);

    // Enable EXTI interrupt.
    EXTI->IMR |= (1u << 2u);

    // Setup NVIC.
    NVIC_EnableIRQ (EXTI2_3_IRQn);

    while (1)
    {
        while ( !app_exti_event_on )
        {
        }
        app_exti_event_on = false;

        app_exti_event_times++;
        if ( (app_exti_event_times % 2u) != 0u )
        {

            GPIOB->BSRR = (1u << 3u);// LED2(PB3 pin) off.
        }
        else
        {

            GPIOB->BRR = (1u << 3u);// LED2(PB3 pin) on.
        }
    }
}