pwm波的输出极性不对

L00p

[mw_shl_code=c,true][/mw_shl_code] [mw_shl_code=c,true] GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(GPIOA, &GPIO_InitStructure);[/mw_shl_code] [mw_shl_code=c,true] TIM_TimeBaseStructure.TIM_Period = 26 - 1; TIM_TimeBaseStructure.TIM_Prescaler = 72 - 1; TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Down; TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure); TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; TIM_OCInitStructure.TIM_Pulse = 13; TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset; TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Reset; TIM_OC3Init(TIM2, &TIM_OCInitStructure); TIM_OC3PreloadConfig(TIM2, TIM_OCPreload_Enable); TIM_ARRPreloadConfig(TIM2, ENABLE); NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = TIM2_PREEM_PRIO; NVIC_InitStructure.NVIC_IRQChannelSubPriority = TIM2_SUB_PRIO; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE); TIM_CCxCmd(TIM2, TIM_Channel_3, TIM_CCx_Enable); TIM_Cmd(TIM2, ENABLE);[/mw_shl_code]

我的定时器是这样配置的，但是出来后的pwm波，好像极性不对。

实际情况是A的波形，但是按照这种配置不应该是B的波形吗？

—孤独￥的风

TIMx_CCMR和TIMx_CCER配置才能控制波形的极性：例如CH1中，PWM模式1 － 在向上计数时，一旦TIMx_CNT<TIMx_CCR1 时通道1 为有效电平，否则为
无效电平；在向下计数时，一旦TIMx_CNT>TIMx_CCR1 时通道1 为无效电平(OC1REF=0)，否则为有效电平(OC1REF=1)。这其中的有效电平不是指
高电平而是由TIMx_CCER寄存器对应的CC1P位设置的。

L00p

用的Stm32F103的芯片。

L00p

好吧，输出的极性是对的。但是默认是低电平不应该啊

L00p

回复【4楼】—孤独￥的风:
---------------------------------
CC1P = 0时，高电平有效
我设置的就是高电平有效。

我只是不知道为什么我设置后，默认的是低电平。就是A那种波形。