STM32之TIM3_PWM程序

简介：STM32之TIM3_PWM程序详解：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。

原理图：

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=324M

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;}

}