TIM_CCxChannelCmd函数无法关闭互补通道输出

应用：TIM1比较输出生成步进电机的控制脉冲，硬件上就是一路，恰好就是TIM1的ch3N，是在一个互补通道上，所以才会遇到这个小问题。

TIM_CCxChannelCmd(TIM1, TIM_CHANNEL_3, TIM_CCxN_ENABLE);

该函数可以打开互补通道。而以下代码毫无作用：

TIM_CCxChannelCmd(TIM1, TIM_CHANNEL_3, TIM_CCxN_DISABLE);

实际上互补通道不应该使用此函数，而是：

static void TIM_CCxNChannelCmd(TIM_TypeDef *TIMx, uint32_t Channel, uint32_t ChannelNState)

该函数是【stm32f0xx_hal_tim_ex.c】中的静态函数！而TIM_CCxChannelCmd在【stm32f0xx_hal_tim.c】中！！

可以用“HAL_TIMEx_PWMN_Stop(&htim1,TIM_CHANNEL_3);”替代，但是还是照抄重写一个把：

/**
  * @brief  Enables or disables the TIM Capture Compare Channel xN.
  * @param  TIMx to select the TIM peripheral
  * @param  Channel specifies the TIM Channel
  *          This parameter can be one of the following values:
  *            @arg TIM_CHANNEL_1: TIM Channel 1
  *            @arg TIM_CHANNEL_2: TIM Channel 2
  *            @arg TIM_CHANNEL_3: TIM Channel 3
  * @param  ChannelNState specifies the TIM Channel CCxNE bit new state.
  *          This parameter can be: TIM_CCxN_ENABLE or TIM_CCxN_Disable.
  * @retval None
  */
void TIM_CCxNCmd(TIM_TypeDef *TIMx, uint32_t Channel, uint32_t ChannelNState)
{
  uint32_t tmp;
 
  tmp = TIM_CCER_CC1NE << (Channel & 0x1FU); /* 0x1FU = 31 bits max shift */
 
  /* Reset the CCxNE Bit */
  TIMx->CCER &=  ~tmp;
 
  /* Set or reset the CCxNE Bit */
  TIMx->CCER |= (uint32_t)(ChannelNState << (Channel & 0x1FU)); /* 0x1FU = 31 bits max shift */
}