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定时器是我们在嵌入式单片机里应用最广泛的外设。使用定时器的水平高低也决定着整个项目实施的水平高低。本次版主给大家带了使用TIM3定时器产生PWM示例。例程主要使用TIM3来产生40K频率的方波，占空比通过按键可调，按键按下时，占空比增加。

实例还是比较简单的，版主就不再多多叙述，大家直接看源代码吧！

源代码：

/**
  * @brief  tim3 pwm 40KHz
  * @param  
  * @retval 
  * @date   2015-03-31
  * @note   
  */

void TIM3PWM(void)
{
  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
  NVIC_InitTypeDef NVIC_InitStructure;
  GPIO_InitTypeDef GPIO_InitStructure;
  TIM_OCInitTypeDef  TIM_OCInitStructure;


  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
  
  /* GPIOA Configuration: TIM3 CH4 (PB1) */
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP ;
  GPIO_Init(GPIOB, &GPIO_InitStructure); 
  
  GPIO_PinAFConfig(GPIOB, GPIO_PinSource1, GPIO_AF_1);


  /* Enable the TIM3 gloabal Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = TIM3_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

  TIM_TimeBaseStructure.TIM_Prescaler = 0;  /*!< 分频为48MHz */
  TIM_TimeBaseStructure.TIM_Period = 1199;  /*!< 40KHz频率 */
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  
  TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
  
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = gCCR4_Val;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
  
  TIM_OC4Init(TIM3, &TIM_OCInitStructure);
  TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Disable); 
  
  TIM_Cmd(TIM3, ENABLE);
}


/**
  * @brief  key check
  * @param  
  * @retval 
  * @date   2015-03-28
  * @note   
  */

void KeyCheck(void)
{
  bool KeyStatus;
  KeyStatus = KeyScan(0);
  
  switch(gKeyStatus)
  {
    case 0:  /*!< 空闲状态 */
    {
      if(KeyStatus == true)
      {
        gKeyStatus = 1;
      }
      else
      {
        gKeyStatus = 0;
        LedOff(0);
        gSendCmdStatus = 0;
      }
      break;
    }
    case 1:  /*!< 消抖状态 */
    {
      if(KeyStatus == true)
      {
        gKeyCnt = 5;
        gKeyStatus = 2;
      }
      else
      {
        gKeyCnt = 0;
        gKeyStatus = 0;
      }
      break;
    }
    case 2:  /*!< 按下状态 */
    {
      if(KeyStatus == true)
      {
        if(gKeyCnt == 0)
        {
          //按键按下执行内容
          LedOn(0);
          gSendCmdStatus |= 0x0F;
          
        }
        else
        {
          gKeyStatus = 2;
        }
      }
      else
      {
        gKeyCnt = 0;
        gKeyStatus = 0;
      }
      break;
    }
    case 3:  /*!< 确认按下 */
    {
      LedOn(0);
      break;
    }
    default: gKeyStatus = 0;
  }

}

/**
  * @brief  uart_int
  * @param  
  * @retval 
  * @date   2015-03-29
  * @note   发送使用DMA方式，接收使用中断
  */

void UartConfig(uint32_t band)
{
  USART_InitTypeDef USART_InitStructure;
  GPIO_InitTypeDef  GPIO_InitStructure;
  NVIC_InitTypeDef NVIC_InitStructure;
  DMA_InitTypeDef  DMA_InitStructure;

  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
  RCC_APB2PeriphClockCmd (RCC_APB2Periph_USART1, ENABLE);
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

  
  /* Connect pin to Periph */
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource9, GPIO_AF_1);    
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource10, GPIO_AF_1); 
  
  /* Configure pins as AF pushpull */
  GPIO_InitStructure.GPIO_Pin     = GPIO_Pin_9 | GPIO_Pin_10;
  GPIO_InitStructure.GPIO_Mode    = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed   = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType   = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd    = GPIO_PuPd_NOPULL; 
    
  GPIO_Init(GPIOA, &GPIO_InitStructure); 
  
  USART_InitStructure.USART_BaudRate = band;
  USART_InitStructure.USART_WordLength = USART_WordLength_8b;
  USART_InitStructure.USART_StopBits = USART_StopBits_1;
  USART_InitStructure.USART_Parity = USART_Parity_No;
  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
  
  USART_Init(USART1, &USART_InitStructure);
  
  /* NVIC configuration */
  /* Enable the USARTx Interrupt */
  NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);

  USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);
  
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;

  DMA_DeInit(DMA1_Channel2);
  DMA_InitStructure.DMA_PeripheralBaseAddr = USART1_TDR_ADDRESS;
  DMA_InitStructure.DMA_BufferSize = (uint16_t)256;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)(&gSendBuf[0]);
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
  DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
  
  DMA_Init(DMA1_Channel2, &DMA_InitStructure);

  USART_DMACmd(USART1, USART_DMAReq_Tx, ENABLE);
  USART_Cmd(USART1, ENABLE);
}

void main(void)
{
  uint16_t i;
  int8_t Str[] = "hello EEPW\r\n";
  gKeyStatus = 0;
  bspInit();
  gCntLed[0] = 500;
  gCntLed[1] = 500;
  TxIndex = 0;
  gSendCnt = 12;
  gRcvBuf[0] = 100;
  gCCR4_Val = 99;
  
  for(i = 0; i < gSendCnt; i++)
  {
    gSendBuf[i] = Str[i];
  }  
  UartConfig(115200);  
  if (SysTick_Config(48000)) //参数为系统时钟的向上溢出值，此配置为48000，即1ms中断一次
  {
    /* Capture error */ 
    while (1);
  }
  
  TIM3PWM();
  
  while(1)
  {
    if(gCntLed[1] == 0)
    {
      LedToggle(1);
      gCntLed[1] = gRcvBuf[0] * 4;
    }
    KeyCheck();
    
    if(gSendCmdStatus > 0)
    {
      if(gSendCmdStatus < 0x10)
      {
        gCCR4_Val = gCCR4_Val + 100;
        if(gCCR4_Val > 1000)
        {
          gCCR4_Val = 0;
        }
        TIM_SetCompare4(TIM3, gCCR4_Val);
        DMA_Cmd(DMA1_Channel2, DISABLE);
        DMA_SetCurrDataCounter(DMA1_Channel2, gSendCnt);
        DMA_Cmd(DMA1_Channel2, ENABLE);
        gSendCmdStatus |= 0xF0;
      }
    }

  }
}

/**
  * @brief  SysTick_Handler的中断入口函数
  * @param  
  * @retval 
  * @date   2014-11-23
  * @note   
  */

void SysTick_Handler(void)
{
  if(gCntLed[0] > 0)
  {
    gCntLed[0]--;
  }
  else
  {
    gCntLed[0] = 0;
  }
  
  if(gCntLed[1] > 0)
  {
    gCntLed[1]--;
  }
  else
  {
    gCntLed[1] = 0;
  }
  
  if(gKeyCnt > 0)
  {
    gKeyCnt--;
  }
  else
  {
    gKeyCnt = 0;
  }
}

/**
  * @brief  USART1_Handler的中断入口函数
  * @param  
  * @retval 
  * @date   2015-03-29
  * @note   
  */

void USART1_IRQHandler(void)
{
  if (USART_GetITStatus(USART1, USART_IT_RXNE) == SET)
  {
    gRcvBuf[0] = USART_ReceiveData(USART1);

  }
}

工程文件：

exp08_TIM3PWM.zip