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求救啊香主进来看看我的TIM8为什么更新如此的慢

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i198581|  楼主 | 2011-3-22 14:20 | 只看该作者 回帖奖励 |倒序浏览 |阅读模式
现在问题是我将TIM8设置为PWM输出。每次直接设置 TIM8_ARR TIM8_CCR1
总是等4到5秒才看到输出频率变化,为什么没有设置完后就生效呢。
下面是代码TIM8初始化
void TIM8_Configuration(void) //模拟频率(PC7)
{
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure,TIM_BaseInitStructure;
    TIM_TimeBaseInitTypeDef  timInitStruct;
    TIM_OCInitTypeDef        TIM_OCInitStructure;
    TIM_ICInitTypeDef        TIM_ICInitStructure;
TIM_BDTRInitTypeDef      TIM_BDTRInitStructure;
  TIM_DeInit(TIM8);
  ///////////////////////////////////////////////////////////////////////////////////
  //下面代码是的配置是让TIM8产生PWM输出
  ///////////////////////////////////////////////////////////////////////////////////

  TIM_ClearFlag(TIM8, TIM_FLAG_Update);        //清除更新标志位  
  TIM_TimeBaseStructure.TIM_Period =2000;// 2000;      //TIM_Period设置也是TIM_Period =(Prescaler +1) ;计数器向上计数到1000后产生更新事件,计数值归零,设定的最大计数值2000,最大计数值是0xffff
  TIM_TimeBaseStructure.TIM_Prescaler = 3599;     //时钟分频3599TIM2时钟 = 72Mhz / (3599 +1)= 20khz
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;     // 时钟分割
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Down;  //TIM_CounterMode_Up计数方向向上计数
// TIM_BaseInitStructure.TIM_RepetitionCounter = 0; //TIM_RepetitionCounter(TIM1_RCR)=0,每次向上溢出都产生更新事件
  TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);
   // Output Compare Toggle Mode configuration: Channel1 (PC6)
//TIM1_OC1模块设置(设置1通道占空比)
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
    TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
    TIM_OCInitStructure.TIM_Pulse = 120;
    TIM_OC1Init(TIM8, &TIM_OCInitStructure);
    //启用CCR1寄存器的影子寄存器(直到产生更新事件才更改设置)
    TIM_OC1PreloadConfig(TIM8, TIM_OCPreload_Enable);

    //TIM2_OC2模块设置(设置通道2占空比)(PC7)
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Disable;
TIM_OCInitStructure.TIM_OCPolarity =   TIM_OCPolarity_Low;  // TIM_OCPolarity_High ; //高电平
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_Low;
    TIM_OCInitStructure.TIM_Pulse = 680;
    TIM_OC2Init(TIM8, &TIM_OCInitStructure);
    //启用CCR2寄存器的影子寄存器(直到产生更新事件才更改设置)
    TIM_OC2PreloadConfig(TIM8, TIM_OCPreload_Enable);
    //TIM2_OC3模块设置(设置2通道占空比)
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 500;
    TIM_OC3Init(TIM8, &TIM_OCInitStructure);
    //启用CCR2寄存器的影子寄存器(直到产生更新事件才更改设置)
    TIM_OC3PreloadConfig(TIM8, TIM_OCPreload_Enable);
    //TIM2_OC4模块设置(设置2通道占空比)
    TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
    TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
    TIM_OCInitStructure.TIM_Pulse = 500;
    TIM_OC4Init(TIM8, &TIM_OCInitStructure);
    //启用CCR2寄存器的影子寄存器(直到产生更新事件才更改设置)
    TIM_OC4PreloadConfig(TIM8, TIM_OCPreload_Enable);  
   
    //死区设置
    TIM_BDTRInitStructure.TIM_OSSRState = TIM_OSSRState_Enable;
    TIM_BDTRInitStructure.TIM_OSSIState = TIM_OSSIState_Enable;
    TIM_BDTRInitStructure.TIM_LOCKLevel = TIM_LOCKLevel_OFF;
    TIM_BDTRInitStructure.TIM_DeadTime = 0x90; //这里调整死区大小0-0xff
    TIM_BDTRInitStructure.TIM_Break = TIM_Break_Disable;
    TIM_BDTRInitStructure.TIM_BreakPolarity = TIM_BreakPolarity_High;
    TIM_BDTRInitStructure.TIM_AutomaticOutput = TIM_AutomaticOutput_Enable;
    TIM_BDTRConfig(TIM8, &TIM_BDTRInitStructure);
// TIM_ITConfig(TIM8, TIM_IT_CC1 | TIM_IT_CC2 | TIM_IT_CC3 | TIM_IT_CC4, ENABLE);//使能定时器的中断
  TIM_ARRPreloadConfig(TIM8, ENABLE);  // 使能或禁用TIMx外设ARR预载寄存器.
  TIM_CtrlPWMOutputs(TIM8,ENABLE);    //  使能或禁用TIM外围主输出
  /////////////////////////////////////////////////////////////////////////////////////////
  //关闭N通道的比较输出
  TIM_CCxNCmd(TIM8,TIM_Channel_1,TIM_CCxN_Disable);
  TIM_CCxNCmd(TIM8,TIM_Channel_2,TIM_CCxN_Disable);
  TIM_CCxNCmd(TIM8,TIM_Channel_3,TIM_CCxN_Disable);
  TIM_CCxNCmd(TIM8,TIM_Channel_4,TIM_CCxN_Disable);
  ///////////////////////////////////////////////////////////////////////////////////////////
  TIM_Cmd(TIM8, ENABLE);       //TIM1 enable counter
沙发
i198581|  楼主 | 2011-3-22 14:22 | 只看该作者
补充下定时器时钟是设置为72MHz。

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板凳
i198581|  楼主 | 2011-3-22 14:28 | 只看该作者
这是TIM8寄存器的定义
#define TIM8_ARR   (volatile unsigned long *) (TIM8_BASE+0x02c)//PWM输出周期
#define TIM8_CCR4  (volatile unsigned long *) (TIM8_BASE+0x040)//占空长度
#define TIM8_CCR1  (volatile unsigned long *) (TIM8_BASE+0x034)//占空长度
#define TIM8_CCR2  (volatile unsigned long *) (TIM8_BASE+0x038)//占空长度
下面是在主程序里设置TIM8_ARR   与 TIM8_CCR1(输出频率在10HZ到500hz)
*TIM8_ARR =tmp-1;//PWM输出周期
*TIM8_CCR1=tmp/10;//占空长度

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