STM32 PWM波比较输出

关键配置

对应GPIO

NVIC中断管理

定时器初始化

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

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 72MHz72MHz，则计数频率为：

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。

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 1M1M，想要得到10 K 10K10K，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 

1000

1M

 =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;

}

  }

}