定时器TIM8有点问题，请求援助

an544 · 发表于 2016-6-13 17:59:31

我用高级定时器TIM8做编码器的读取，初始化的时候，已经让TIM8->CNT=0，电机转动的同时，在while(1)中不断读取TIM8->CNT的值。结果显示在没有通过串口中断给STM32发送指令之前，TIM8->CNT一直是0，发送指令的一瞬间，TIM8->CNT从65535开始减少。TIM8初始化的时候明明是向上计数啊。。。。求助各路大神帮忙,是不是我TIM8配置有问题？！

代码如下：
int main(void)
{
u8 str[256], i, n;
      int a,count=0;
      delay_init();
      NVIC_Configuration();
      uart_init(72,9600);
IO_Init();
TIM1_PWM_Init(7199,4);
      TIM8_Init();//定时器编码器接口初始化
      coderInit();
      while(1){
      a =TIM8->CNT;
      n = sprintf(str, "count=%d\n", a);
            for (i = 0; i < n; i++)
            {
                  USART_SendData(USART1,str[i]);
                  delay_ms(2);
            }
      }
void TIM8_Init()
{
GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_ICInitTypeDef TIM_ICInitStructure;
NVIC_InitTypeDef NVIC_InitStructure;
TIM_DeInit(TIM8);
//PB6 ch1  A,PB7 ch2
RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM8, ENABLE);//使能TIM4时钟
RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);//使能GPIOA时钟

GPIO_StructInit(&GPIO_InitStructure);//将GPIO_InitStruct中的参数按缺省值输入
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_7;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;//PA6 PA7浮空输入
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOC, &GPIO_InitStructure);

NVIC_InitStructure.NVIC_IRQChannel =TIM8_UP_IRQn ;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);

TIM_DeInit(TIM8);
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Period =65535;// 199*4;  //设定计数器重装值 TIMx_ARR = 359*4
TIM_TimeBaseStructure.TIM_Prescaler = 0; //TIM3时钟预分频值
TIM_TimeBaseStructure.TIM_ClockDivision =TIM_CKD_DIV1 ;//设置时钟分割 T_dts = T_ck_int
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; //TIM向上计数
TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);

TIM_EncoderInterfaceConfig(TIM8, TIM_EncoderMode_TI12, TIM_ICPolarity_BothEdge ,TIM_ICPolarity_BothEdge);//使用编码器模式3，上升下降都计数
TIM_ICStructInit(&TIM_ICInitStructure);//将结构体中的内容缺省输入
TIM_ICInitStructure.TIM_ICFilter = 6;  //选择输入比较滤波器
TIM_ICInit(TIM8, &TIM_ICInitStructure);//将TIM_ICInitStructure中的指定参数初始化TIM3

TIM_ClearFlag(TIM8, TIM_FLAG_Update);//清除TIM3的更新标志位
TIM_ITConfig(TIM8, TIM_IT_Update, ENABLE);//运行更新中断
TIM8->CNT = 0;
TIM_Cmd(TIM8, ENABLE); //启动TIM4定时器

void TIM8_UP_IRQHandler(void)
{

if(TIM8->SR&0x0001)//溢出中断
{
}
TIM8->SR&=~(1<<0);//清除中断标志位
}