STM32之旅7——PWMN

stm32可以使用定时器输出PWM，每一个定时器都有对应的通道，下面是使用hal库产生PWM的步骤：
1、配置系统时钟

2、选择定时器及对应的通道

3、配置定时器及通道

4、业务代码
（1）启动PWM：HAL库里面只有这么一个函数知道调用了这个函数就可以产生PWM

/**
  * @brief  Starts the PWM signal generation.
  * @param  htim TIM handle
  * @param  Channel TIM Channels to be enabled
  *          This parameter can be one of the following values:
  *            @arg TIM_CHANNEL_1: TIM Channel 1 selected
  *            @arg TIM_CHANNEL_2: TIM Channel 2 selected
  *            @arg TIM_CHANNEL_3: TIM Channel 3 selected
  *            @arg TIM_CHANNEL_4: TIM Channel 4 selected
  * @retval HAL status
  */
HAL_StatusTypeDef HAL_TIM_PWM_Start(TIM_HandleTypeDef *htim, uint32_t Channel)
{
  uint32_t tmpsmcr;

  /* Check the parameters */
  assert_param(IS_TIM_CCX_INSTANCE(htim->Instance, Channel));

  /* Enable the Capture compare channel */
  TIM_CCxChannelCmd(htim->Instance, Channel, TIM_CCx_ENABLE);

  if (IS_TIM_BREAK_INSTANCE(htim->Instance) != RESET)
  {
    /* Enable the main output */
    __HAL_TIM_MOE_ENABLE(htim);
  }

  /* Enable the Peripheral, except in trigger mode where enable is automatically done with trigger */
  tmpsmcr = htim->Instance->SMCR & TIM_SMCR_SMS;
  if (!IS_TIM_SLAVEMODE_TRIGGER_ENABLED(tmpsmcr))
  {
    __HAL_TIM_ENABLE(htim);
  }

  /* Return function status */
  return HAL_OK;
}

另外像CH1N、CH2N、CH3N、CH4N这种互补通道，在生成工程之后还要修改其里面的一个函数：

TIM_OCx_SetConfig()；                   //(x = 1, 2, 3, 4)

把那一行换成

tmpccer |= TIM_CCER_CC1NE;

（2）设置占空比的函数（其实是一个宏）：

__HAL_TIM_SET_COMPARE(__HANDLE__, __CHANNEL__, __COMPARE__) 

如：

	__HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_2, 80);           //设置TIM_CHANNEL_2N占空比为80
	__HAL_TIM_SET_COMPARE(&htim1, TIM_CHANNEL_3, 50);            //设置TIM_CHANNEL_3N占空比为60
	HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_2);                    //开始
	HAL_TIM_PWM_Start(&htim1, TIM_CHANNEL_3);