PWM输出，呼吸灯

一、初始化GPIO

使用PB1,查芯片手册对应TIM3_CH4

1.     GPIO_InitTypeDef GPIO_InitStructure;
   
2.     RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);
   
3.     RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);
   
4. 
   
5.     
   
6.     GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
   
7.     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
   
8.     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
   
9.     
   
10.     GPIO_Init(GPIOB, &GPIO_InitStructure);

二、初始化TIM和PWM

1.     TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
   
2.     TIM_OCInitTypeDef TIM_OCInitStructure;
   
3. 
   
4.     /* 周期1000 */
   
5.     TIM_TimeBaseStructure.TIM_Period = 999;
   
6.     /* 定时器时间间隔1微秒 */
   
7.     TIM_TimeBaseStructure.TIM_Prescaler = 0;
   
8.     TIM_TimeBaseStructure.TIM_ClockDivision = 0;
   
9.     /* 向上计数 */
   
10.     TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
    
11.     /* 配置 */
    
12.     TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
    
13.     
    
14.     /* 选择PWM1模式 */
    
15.     TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    
16.     /* 允许输出模式 */
    
17.     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;    
    
18.     /* 匹配值 */
    
19.     TIM_OCInitStructure.TIM_Pulse = 1000;    
    
20.     /* 设置小于匹配值时为高电平 */
    
21.     TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    
22.     /* 使能通道1 */
    
23.     TIM_OC4Init(TIM3, &TIM_OCInitStructure);    
    
24.     
    
25.     TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);
    
26.     TIM_ARRPreloadConfig(TIM3, ENABLE);
    
27.     TIM_Cmd(TIM3, ENABLE);

三、main函数部分

通过修改CCRx寄存器，改变占空比。从而调整电流大小

1. while(1)
   
2. {
   
3.         if(CCR3_Val >=0 && CCR3_Val <= 1000)
   
4.         {
   
5.             CCR3_Val -= 50;
   
6.             Delay(1);
   
7.         }
   
8.         else
   
9.         {
   
10.             CCR3_Val = 1000;
    
11.             Delay(1);
    
12.         }
    
13.         TIM3->CCR4 = CCR3_Val;
    
14.         Delay(1);
    
15. }