PWM输出配置

1）使能定时器3和IO口时钟

       RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE); //使能定时器3

RCC_APB1PeriphClockCmd(RCC_APB2Periph_GPIOB | RCC_APB2Periph_AFIO, ENABLE);//使能GPIOB和AFIO复用

2）初始化IO口

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8; //TIM_CH1

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //复用推挽输出

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

3）开启AFIO时钟，重映射

GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3, ENABLE);

4）初始化定时器，ARR、PSC等

TIM_TimeBaseStructure.TIM_Period = arr;

TIM_TimeBaseStructure.TIM_Prescaler =psc;

TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; 

TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

5）初始化输出比较参数

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

TIM_OC2Init(TIM3, &TIM_OCInitStructure); 

6）使能预装载寄存器

TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);  //使能TIM3在CCR2上的预装载寄存器

7）使能定时器TIM3

TIM_Cmd(TIM3, ENABLE); 

8）改变CCR（改变占空比）