我使用TIM8的通道3和4，输出的PWM信号为什么不是0-3.3V的信号呢？

jubangyu · 发表于 2020-6-24 11:18:10

求助，占空比低的时候还接近0-3.3V的脉冲，等占空比提高，信号就向下移动了，这是怎么回事呢？
微信图片_20200624111512.jpg

初始化代码如下：
void TIM8_PWM_Init(u16 arr,u16 psc)
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8, ENABLE); //
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC , ENABLE);  //使能GPIO外设时钟使能 |RCC_APB2Periph_AFIO


//设置该引脚为复用输出功能,输出TIM8 CH4的PWM脉冲波形
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8|GPIO_Pin_9; //TIM8_Ch4
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;    //复用推挽输出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC, &GPIO_InitStructure);

TIM_DeInit(TIM8);

/* Time Base configuration */
TIM_TimeBaseStructure.TIM_Period          = arr;
TIM_TimeBaseStructure.TIM_Prescaler       = psc;
TIM_TimeBaseStructure.TIM_CounterMode    = TIM_CounterMode_Up;
TIM_TimeBaseStructure.TIM_ClockDivision    = 0;
TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);

TIM_OCInitStructure.TIM_OCMode          = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OutputState       = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse                = 0;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;

//新加代码20200624
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset ;
TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Reset;

TIM_OC3Init(TIM8, &TIM_OCInitStructure);
TIM_OC4Init(TIM8, &TIM_OCInitStructure);

TIM_CtrlPWMOutputs(TIM8,ENABLE);

TIM_OC3PreloadConfig(TIM8, TIM_OCPreload_Enable);
TIM_OC4PreloadConfig(TIM8, TIM_OCPreload_Enable);

TIM_ARRPreloadConfig(TIM8, ENABLE);

TIM_Cmd(TIM8, ENABLE);

TIM_SetCompare3(TIM8, 300);
TIM_SetCompare4(TIM8, 300);
}