实验原理：
通过STM32的一个GPIO口来驱动LED灯，设定GPIO为推挽输出模式，采用灌电流的方式与LED连接，
输出高电平LED灭，输出低电平LED亮，通过通用定时器TIM3实现500ms定时，每500ms变换一次LED的状态。
示例截图：
源代码下载链接：
链接：https://pan.baidu.com/s/1eTSNL54 密码：1ypb
GMT43购买链接：
核心代码：
static int initialize(void)
{
TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStructure;
NVIC_InitTypeDef NVIC_InitStructure; RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE); TIM_TimeBaseInitStructure.TIM_Period = 4999;
TIM_TimeBaseInitStructure.TIM_Prescaler = 8399;
TIM_TimeBaseInitStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseInitStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3,&TIM_TimeBaseInitStructure); TIM_ITConfig(TIM3,TIM_IT_Update,ENABLE); NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x01;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x03;
NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
NVIC_Init(&NVIC_InitStructure); return 0;
}
void TIM3_IRQHandler(void)
{
static int timer_counter = 0; if(TIM_GetITStatus(TIM3,TIM_IT_Update)==SET)
{
if(timer_counter % 2 == 0){
LED_OFF;
}else{
LED_ON;
}
}else{
LED_OFF;
}
timer_counter ++;
TIM_ClearITPendingBit(TIM3,TIM_IT_Update);
}