TIM4的PWM输出,被折磨的很痛苦.

aa511950071 · 发表于 2016-3-21 21:09:28

//定时器4 pwm输出
void TIM4_PWM_Init(u16 arr,u16 psc)
{
GPIO_InitTypeDef    GPIO_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef    TIM_OCInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD  | RCC_APB2Periph_AFIO, ENABLE);  //使能GPIO外设和AFIO复用功能模块时钟使能
GPIO_PinRemapConfig(GPIO_Remap_TIM4, ENABLE); //Timer4部分重映射  TIM3_CH2->PB5
//设置该引脚为复用输出功能,输出TIM3 CH2的PWM脉冲波形 GPIOB.5
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12; //TIM_CH2
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //复用推挽输出
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOD, &GPIO_InitStructure);//初始化GPIO

TIM_TimeBaseStructure.TIM_Period    = arr; //设定计数器自动重装值
TIM_TimeBaseStructure.TIM_Prescaler = psc;  //预分频器
TIM_TimeBaseStructure.TIM_ClockDivision = 0; //设置时钟分割:TDTS = Tck_tim
TIM_TimeBaseStructure.TIM_CounterMode  = TIM_CounterMode_Up;  //TIM向上计数模式
TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure); //根据TIM_TimeBaseInitStruct中指定的参数初始化TIMx的时间基数单位
TIM_OCInitStructure.TIM_OCMode    = TIM_OCMode_PWM2;
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //输出极性:TIM输出比较极性高
TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //比较输出使能
TIM_OC1Init(TIM4, &TIM_OCInitStructure);  //根据T指定的参数初始化外设TIM3 OC2
TIM_OC1PreloadConfig(TIM4,TIM_OCPreload_Enable);  //使能TIMx在CCR2上的预装载寄存器

TIM_Cmd(TIM4, ENABLE);  //使能TIMx外设

}

int main(void)
{
  u16 led0pwmval=0;
u8 dir=1;
delay_init();    //延时函数初始化
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); //设置NVIC中断分组2:2位抢占优先级，2位响应优先级
uart_init(115200);  //串口初始化为115200
  LED_Init();       //LED端口初始化
  TIM4_PWM_Init(899,0);  //不分频。PWM频率=72000000/900=80Khz
  while(1)
{
delay_ms(10);
  if(dir)led0pwmval++;
  else led0pwmval--;
if(led0pwmval>300)dir=0;
  if(led0pwmval==0)dir=1;
  TIM_SetCompare2(TIM4,led0pwmval);
}
}

PD12引脚一直显示是高电平,而不是像正点原子实验里面PWM电压是变化的,不知道为什么?查了半天查不出个原因,完全是改的正点原子的PWM实验,只是换了TIM4,复用引脚刀PD12.