STM32之TIM3_PWM程序

只看该作者 · 2023-10-12 09:49

原理图：

调PB5的亮度

头文件及完整例程下载：[size=13.3333px]http://www.51hei.com/f/stm32标准例程库函数.rar

程序分析：

int main(void)
{
unsigned char a=0;
TIM_OCInitTypeDef  TIM3_OCInitStructure;
    RCC_Configuration();
    time_ini();
SysTick_Config(72000);    //配置SYSTICK时钟节拍为1ms一次
    while(1){
    Delay(1);    //延时1ms
TIM3_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;    //PWM模式2
    TIM3_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;    //输出禁止
    TIM3_OCInitStructure.TIM_Pulse = CCR2_Val;    //确定占空比
    TIM3_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
    TIM_OC2Init(TIM3, &TIM3_OCInitStructure);

    /*调整CCR2_Val的值来改变占空比，逐步的控制LED1的亮度, 占空比大过一定值时，
亮度的变化就不明显了，所以CCR2_VAL最大设定到17000*/
if(a==0) CCR2_Val=CCR2_Val+10;
else CCR2_Val=CCR2_Val-10;
if(CCR2_Val>17000){ CCR2_Val=17000; a=1;}
else if(CCR2_Val<200){ CCR2_Val=200; a=0;}
    }

}

时钟初始化打开RCC_APB2Periph_AFIO ，RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOCD| RCC_APB2Periph_GPIOD| RCC_APB2Periph_GPIOE

void RCC_Configuration(void){

  SystemInit();
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOC
    | RCC_APB2Periph_GPIOD| RCC_APB2Periph_GPIOE , ENABLE);
}

配置初始化，初始化PB5为复用输出，TIM3部分映射到PB5,设置PWM的时钟为72M/(3*2400)=10K,初始化TIM3时钟，
占空比为CCR2_Val /(TIM_Period  +1)

void time_ini(void){
  GPIO_InitTypeDef GPIO_InitStructure;
  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; //PB5复用为TIM3的通道2
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(GPIOB, &GPIO_InitStructure);
  /*TIM3局部复用功能开启    在TIM3的局部复用开启时，PB5会被复用为TIM3_CH2*/
  GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3 , ENABLE); //TIM3部分映射到PB5

/*-------------------------------------------------------------------
  TIM3CLK=72MHz  预分频系数Prescaler=2 经过分频定时器时钟为24MHz
  根据公式通道输出占空比=TIM3_CCR2/(TIM_Period+1),可以得到TIM_Pulse的计数值
  捕获/比较寄存器2 TIM3_CCR2= CCR2_Val
  -------------------------------------------------------------------*/
  TIM3_TimeBaseStructure.TIM_Prescaler = 2;       //预分频器TIM3_PSC=3      24M
  TIM3_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //计数器向上计数模式 TIM3_CR1[4]=0
  TIM3_TimeBaseStructure.TIM_Period =2399;             //自动重装载寄存器TIM3_APR  确定频率为10KHz
  TIM3_TimeBaseStructure.TIM_ClockDivision = 0x0; //时钟分频因子 TIM3_CR1[9:8]=00
  TIM3_TimeBaseStructure.TIM_RepetitionCounter = 0x0;
  TIM_TimeBaseInit(TIM3,&TIM3_TimeBaseStructure); //写TIM3各寄存器参数

  TIM3_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;       //PWM模式2 TIM3_CCMR1[14:12]=111 在向上计数时，
          //一旦TIMx_CNT<TIMx_CCR1时通道1为无效电平，否则为有效电平
  TIM3_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //输入/捕获2输出允许  OC2信号输出到对应的输出引脚PB5
  TIM3_OCInitStructure.TIM_Pulse = CCR2_Val;       //确定占空比，这个值决定了有效电平的时间。
  TIM3_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;       //输出极性  低电平有效 TIM3_CCER[5]=1;

  TIM_OC2Init(TIM3, &TIM3_OCInitStructure);
  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);
  TIM_Cmd(TIM3,ENABLE); //启动定时器3 TIM3_CR1[0]=1;
}

SysTick_Config(72000);    //配置SYSTICK时钟节拍为1ms一次

while(1){
    Delay(1);    //延时1ms
TIM3_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;    //PWM模式2
    TIM3_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;    //输出禁止
    TIM3_OCInitStructure.TIM_Pulse = CCR2_Val;    //确定占空比
    TIM3_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
    TIM_OC2Init(TIM3, &TIM3_OCInitStructure);

    /*调整CCR2_Val的值来改变占空比，逐步的控制LED1的亮度, 占空比大过一定值时，
亮度的变化就不明显了，所以CCR2_VAL最大设定到17000*/
if(a==0) CCR2_Val=CCR2_Val+10;
else CCR2_Val=CCR2_Val-10;
if(CCR2_Val>17000){ CCR2_Val=17000; a=1;}
else if(CCR2_Val<200){ CCR2_Val=200; a=0;}
    }