STM32之TIM3_PWM程序

原理圖：
調(diào)PB5的亮度

 頭文件及完整例程下載：http://www.torrancerestoration.com/f/stm32標(biāo)準(zhǔn)例程庫(kù)函數(shù).rar

程序分析：

} 

時(shí)鐘初始化打開(kāi)RCC_APB2Periph_AFIO ，RCC_APB2Periph_GPIOA | RCC_APB2Periph_GPIOB | RCC_APB2Periph_GPIOCD| RCC_APB2Periph_GPIOD| RCC_APB2Periph_GPIOE

} 

配置初始化，初始化PB5為復(fù)用輸出，TIM3部分映射到PB5,設(shè)置PWM的時(shí)鐘為72M/(3*2400)=10K,初始化TIM3時(shí)鐘，
占空比為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復(fù)用為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局部復(fù)用功能開(kāi)啟 在TIM3的局部復(fù)用開(kāi)啟時(shí)，PB5會(huì)被復(fù)用為TIM3_CH2*/

  GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3 , ENABLE); //TIM3部分映射到PB5  

 

   /*-------------------------------------------------------------------

  TIM3CLK=72MHz  預(yù)分頻系數(shù)Prescaler=2 經(jīng)過(guò)分頻 定時(shí)器時(shí)鐘為24MHz

  根據(jù)公式 通道輸出占空比=TIM3_CCR2/(TIM_Period+1),可以得到TIM_Pulse的計(jì)數(shù)值  

  捕獲/比較寄存器2 TIM3_CCR2= CCR2_Val     

  -------------------------------------------------------------------*/

  TIM3_TimeBaseStructure.TIM_Prescaler = 2;    //預(yù)分頻器TIM3_PSC=3 24M

  TIM3_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //計(jì)數(shù)器向上計(jì)數(shù)模式 TIM3_CR1[4]=0

  TIM3_TimeBaseStructure.TIM_Period =2399;            //自動(dòng)重裝載寄存器TIM3_APR  確定頻率為10KHz     

  TIM3_TimeBaseStructure.TIM_ClockDivision = 0x0; //時(shí)鐘分頻因子 TIM3_CR1[9:8]=00

  TIM3_TimeBaseStructure.TIM_RepetitionCounter = 0x0;

  TIM_TimeBaseInit(TIM3,&TIM3_TimeBaseStructure); //寫TIM3各寄存器參數(shù)

  

  TIM3_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;    //PWM模式2 TIM3_CCMR1[14:12]=111 在向上計(jì)數(shù)時(shí)，

     //一旦TIMx_CNT<TIMx_CCR1時(shí)通道1為無(wú)效電平，否則為有效電平

  TIM3_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;    //輸入/捕獲2輸出允許  OC2信號(hào)輸出到對(duì)應(yīng)的輸出引腳PB5

  TIM3_OCInitStructure.TIM_Pulse = CCR2_Val;    //確定占空比，這個(gè)值決定了有效電平的時(shí)間。

  TIM3_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;    //輸出極性  低電平有效 TIM3_CCER[5]=1;

         

  TIM_OC2Init(TIM3, &TIM3_OCInitStructure);

  TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);

  TIM_Cmd(TIM3,ENABLE); //啟動(dòng)定時(shí)器3 TIM3_CR1[0]=1; 

} 

    SysTick_Config(72000);   //配置SYSTICK時(shí)鐘節(jié)拍為1ms一次

  while(1){

  Delay(1);  //延時(shí)1ms  

TIM3_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;  //PWM模式2 

  TIM3_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;  //輸出禁止        

  TIM3_OCInitStructure.TIM_Pulse = CCR2_Val;  //確定占空比

  TIM3_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; 

  TIM_OC2Init(TIM3, &TIM3_OCInitStructure);

 

  /*調(diào)整CCR2_Val的值來(lái)改變占空比，逐步的控制LED1的亮度, 占空比大過(guò)一定值時(shí)，

亮度的變化就不明顯了，所以CCR2_VAL最大設(shè)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;} 

   }