关键配置

1. 对应GPIO
2. NVIC中断管理
3. 定时器初始化
4. 定时器输出模式TIM_OC初始化（模式为TIM_OCMode_Toggle）

频率与占空比的计算

1. 计数频率的计算
   若使用比较输出，则ARR表示计数的上限，基本无用。计数频率由TIM_Prescaler成员变量配置。若配置TIM_Prescaler=71，输入时钟为 72 M H z 72MHz 72MHz，则计数频率为：
   f = 72 M 72 + 1 = 1 M f=\frac{72M}{72+1}=1M f=72+172M​=1M
2. 计数规则
   当计数器数到CCR所储存的值时，输出电平就会翻转。
3. 频率和占空比的配置
     由计数规律我们可以通过修改CCR值的方法来得到我们想要的频率和占空比。
     比如：计数频率为 1 M 1M 1M，想要得到 10 K 10K 10K，占空比为 80 % 80\% 80%的PWM波。
     令空闲输出电平为0，关闭影子寄存器以便立即赋值。
     当程序开始，立即进入中断，为CCR赋值为20，此时电平为低电平;
     当计数器数过20，翻转电平，变为高电平，再次进入中断，为CCR赋值为20+80；
     当计数器再数80，翻转电平，变为低电平，再次进入中断，为CCR赋值为20+80+20；
   …
   于是可见，数100为一个周期，其中20为低电平，80为高电平。输出PWM波频率 1 M 1000 = 10 K H z \frac{1M}{1000}=10KHz 10001M​=10KHz，占空比 80 % 80\% 80%.

示例代码

从PA6和PA7输出两路PWM；PA6频率为10KHz，占空比为80% ；PA7频率为1KHz，占空比为20%

PWM驱动配置：

void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_AFIO,ENABLE);
  // PA1 PA2
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

  GPIO_Init(GPIOA, &GPIO_InitStructure);
}


void NVIC_Configuration(void)
{
  NVIC_InitTypeDef NVIC_InitStructure;

  /* Enable the TIM3 global Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}


void PWM_Config()
{
	TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
	TIM_OCInitTypeDef  TIM_OCInitStructure;
	
	
	GPIO_Configuration();
	NVIC_Configuration();
	
	RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
  /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = 65535;                // 在TIM_OCMode_Toggle模式下ARR几乎无用
  TIM_TimeBaseStructure.TIM_Prescaler = 71;                // 72分频，计数频率为72M/72=1M
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;//计数方式为向上计数

  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

  /* Output Compare Toggle Mode configuration: Channel1 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = CCR1_Val;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;   // 空闲状态为低电平
  TIM_OC1Init(TIM3, &TIM_OCInitStructure);

  TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Disable);         // 关闭影子寄存器，当给CCR赋值时，即刻赋值

  /* Output Compare Toggle Mode configuration: Channel2 */
  TIM_OCInitStructure.TIM_Pulse = CCR2_Val;

  TIM_OC2Init(TIM3, &TIM_OCInitStructure);

  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Disable);

	TIM_Cmd(TIM3, ENABLE);
	TIM_ITConfig(TIM3, TIM_IT_CC1 | TIM_IT_CC2, ENABLE);
}

中断代码如下:

extern __IO uint16_t CCR1_Val;
extern __IO uint16_t CCR2_Val;
uint16_t capture = 0;
u8 pa6_state=0,pa7_state=0;

float zhankong1=0.2;
float zhankong2=0.2;
void TIM3_IRQHandler(void)
{
  /* TIM3_CH1 toggling with frequency = 10K Hz */
  if (TIM_GetITStatus(TIM3, TIM_IT_CC1) != RESET)
  {
    TIM_ClearITPendingBit(TIM3, TIM_IT_CC1 );
    capture = TIM_GetCapture1(TIM3);
		if(pa6_state ==0)
		{
			TIM_SetCompare1(TIM3, capture + CCR1_Val*zhankong1 );
			pa6_state = 1;
		}
		else
		{
			TIM_SetCompare1(TIM3, capture + CCR1_Val*(1-zhankong1) );
			pa6_state = 0;			
		}
    
  }

  /* TIM3_CH2 toggling with frequency = 1k Hz */
  if (TIM_GetITStatus(TIM3, TIM_IT_CC2) != RESET)
  {
    TIM_ClearITPendingBit(TIM3, TIM_IT_CC2);
    capture = TIM_GetCapture2(TIM3);
		if(pa7_state ==0)
		{
			TIM_SetCompare2(TIM3, capture + CCR2_Val*zhankong2 );
			pa6_state = 1;
		}
		else
		{
			TIM_SetCompare2(TIM3, capture + CCR2_Val*(1-zhankong2) );
			pa6_state = 0;			
		}
  }
}