请大神指教PWM输出一直是低电平

新手报到 · 发表于 2016-5-20 11:10:51

   我用的是战舰开发板stm32f103ZET6，根据原子的PWM输出实验，设计了TIM3的CH2通道的PWM输出，但是无论是软件仿真波形还是连接示波器，都没与信号，请大神看下是不是我的程序有问题呢？这是主函数：
int main(void)
{

SystemInit();
TIM3_PWM_Init();

      while(1)
{
      }
}

这是PWM函数：
void TIM3_PWM_Init()
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7; //TIM_CH2
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIO_InitStructure);

TIM_TimeBaseStructure.TIM_Period =899;
TIM_TimeBaseStructure.TIM_Prescaler =0;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);


TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
TIM_OCInitStructure.TIM_Pulse = 450;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OC2Init(TIM3, &TIM_OCInitStructure);

TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_ARRPreloadConfig(TIM3, ENABLE);

  TIM_Cmd(TIM3, ENABLE);

}