nvic_irq_enable 该怎么使用

`nvic_irq_enable` 是用来使能 Cortex-M 系列处理器中断的函数。具体使用方法如下：

void nvic_irq_enable(IRQn_Type irqn);

其中，`irqn` 参数表示要使能的中断号。例如，要使能 USART1 的中断，可以使用以下代码：

nvic_irq_enable(USART1_IRQn);

需要注意的是，使用 `nvic_irq_enable` 之前需要先初始化相应的中断，并编写中断处理函数。否则使能中断是没有任何意义的。例如，在使用 USART1 中断前，需要先初始化 USART1 并编写 USART1 的中断处理函数。

此外，为了避免中断嵌套问题，使能中断时需要先关闭全局中断，然后再使能指定的中断。例如：

__disable_irq(); // 关闭全局中断
nvic_irq_enable(USART1_IRQn); // 使能 USART1 中断
__enable_irq(); // 开启全局中断

相关问题

nvic_irq_enable

nvic_irq_enable is a function in the C programming language that enables interrupts for a specific interrupt request line (IRQ) in a microcontroller. The function is typically used in embedded systems programming to allow the microcontroller to respond to external events or signals in real-time.

The function takes an argument that specifies the IRQ line number to be enabled. Once the function is executed, the microcontroller's interrupt controller will be configured to allow interrupts on the specified line. This means that when an interrupt signal is received on that line, the microcontroller will pause its current task and jump to the interrupt service routine (ISR) associated with that line.

Here is an example of how nvic_irq_enable might be used in a program:

#include <stdio.h>
#include "stm32f4xx.h" // includes the appropriate header file for the specific microcontroller being used

void EXTI0_IRQHandler(void) // ISR for EXTI0 (external interrupt on line 0)
{
    printf("External interrupt on line 0 has occurred!\n");
}

int main(void)
{
    // enable clock for GPIO and EXTI peripherals
    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_SYSCFG, ENABLE);

    // configure GPIO pin as input with interrupt
    GPIO_InitTypeDef GPIO_InitStruct;
    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_0;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IN;
    GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
    GPIO_Init(GPIOA, &GPIO_InitStruct);

    // configure EXTI line for GPIO pin
    SYSCFG_EXTILineConfig(EXTI_PortSourceGPIOA, EXTI_PinSource0);

    EXTI_InitTypeDef EXTI_InitStruct;
    EXTI_InitStruct.EXTI_Line = EXTI_Line0;
    EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Rising;
    EXTI_InitStruct.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStruct);

    // enable interrupt for EXTI0 line
    NVIC_EnableIRQ(EXTI0_IRQn);

    while(1) {
        // main program loop
    }

    return 0;
}

In this example, the program configures an external interrupt on GPIO pin 0 of port A on an STM32F4 microcontroller. The nvic_irq_enable function is used to enable interrupts for EXTI line 0, which is associated with the GPIO pin. When the button attached to the pin is pressed, an interrupt signal is generated and the program jumps to the EXTI0_IRQHandler function, which prints a message to the console.

nvic_irq_enable(uint8_t nvic_irq, uint8_t nvic_irq_pre_priority, uint8_t nvic_irq_sub_priority)

nvic_irq_enable函数用于使能指定的中断，并设置中断的优先级。参数`nvic_irq`是要使能的中断编号，`nvic_irq_pre_priority`是中断的抢占优先级，`nvic_irq_sub_priority`是中断的子优先级。

函数实现的伪代码如下：

void nvic_irq_enable(uint8_t nvic_irq, uint8_t nvic_irq_pre_priority, uint8_t nvic_irq_sub_priority) {
    // 设置中断的抢占优先级和子优先级
    NVIC_SetPriority(nvic_irq, NVIC_EncodePriority(NVIC_GetPriorityGrouping(), nvic_irq_pre_priority, nvic_irq_sub_priority));
    
    // 使能中断
    NVIC_EnableIRQ(nvic_irq);
}