定时器计数之怪状

只看该作者 · 2011-8-3 10:32

本帖最后由 siatliuliu 于 2011-8-3 10:36 编辑

平台：火牛开发板STM32F103VBT6  MDK3.8
功能：
1.TIM1 PWM2方式产生频率变化的脉冲
2.TIM2定时每5ms 在更新中断中改变TIM1的频率（ARR）,打印出TIM1在上一个5ms周期里的脉冲数。

现象及问题：
通过示波器可以看到：TIM1输出脉冲每隔5ms 频率按设定的频率变化，问题是计数不准确(如下)。

第n周期第1&2方式脉冲数  第3方式脉冲数  理论脉冲数 TIM1频率
nStep : 1, pulseNum : 6       506          10       2k
nStep : 2, pulseNum : 11       21          20       4k
nStep : 3, pulseNum : 21       46          40       8k
nStep : 4, pulseNum : 42       92          80       16k
nStep : 5, pulseNum : 47    128          90       18k
nStep : 6, pulseNum : 52    142          100       20k
nStep : 7 ,pulseNum : 78    187          150       30k
nStep : 8, pulseNum : 104    263          200       40k
nStep : 9, pulseNum : 125    337          250       50k
nStep : 0, pulseNum : 250    680          500       100k

计数方式：
1.在TIM1的更新中断里计数（算不上严格意义上的计数，只是验证一下）
/* * @file TIM/
/stm32f10x_it.c  **************************************************************/
#include "stm32f10x_it.h"

//对应频率：2k, 4k, 8k, 16k, 18k, 20k, 30k, 40k, 50k, 100k
uint16_t ARR_Buffer[10] = {36000, 18000, 9000, 4500, 4000, 3600, 2400, 1800, 1440, 720};
u32 nStep= 0 ;
u32 pulseNum = 0;

//TIM1 计脉冲数
void TIM1_UP_IRQHandler(void)
{  if (TIM_GetITStatus(TIM1, TIM_IT_Update) != RESET)
  {
   TIM_ClearITPendingBit(TIM1, TIM_IT_Update );
   pulseNum++;                      //计脉冲数
  }
}

//TIM2 5ms中断计时，更改TIM1频率，打印上一阶段脉冲数
void TIM2_IRQHandler(void){
  if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
  {
      TIM_ClearITPendingBit(TIM2, TIM_IT_Update );
         TIM1->CCR1 =  ARR_Buffer[nStep] / 2;    //更改TIM1占空比
         TIM1->ARR = ARR_Buffer[nStep];       //更改TIM1脉冲频率
      printf("\nnStep : %d,pulseNum : %d\n", nStep, pulseNum);  //打印上个5ms TIM1的脉冲数

      pulseNum = 0;                   //脉冲数清零
      nStep++;

      if(nStep >9)                      //10个一循环
         nStep = 0;
  }
}

/* main.c *********************************************************************************/

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;
TIM_ICInitTypeDef  TIM_ICInitStructure;
ErrorStatus HSEStartUpStatus;

int main(void)
{
  /* System Clocks Configuration */
  RCC_Configuration();

  /* GPIO Configuration */
  GPIO_Configuration();

  NVIC_Configuration();

/*USART Configuration */
COM_Init();

  /* TIM1 Peripheral Configuration --------------------------------------------*/
  /* Time Base configuration */
  TIM_TimeBaseStructure.TIM_Prescaler = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = 36000;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;

  TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);

  /* Channel 3 Configuration in PWM mode */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 18000;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low;
  TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_Low;
  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
  TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Reset;

  TIM_OC1Init(TIM1, &TIM_OCInitStructure);
  TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable);
  TIM_ARRPreloadConfig(TIM1, ENABLE);

  //TIM2产生5ms中断计时。
  TIM_DeInit(TIM2);

  TIM_TimeBaseStructure.TIM_Period = 7199;
  TIM_TimeBaseStructure.TIM_Prescaler = 24;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

  TIM_CCPreloadControl(TIM1, ENABLE);

  TIM_ClearFlag(TIM1, TIM_FLAG_Update);
  TIM_ClearFlag(TIM2, TIM_FLAG_Update);

TIM_ITConfig(TIM1, TIM_IT_Update, ENABLE);
TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);

  /* TIM1 counter enable */
  TIM_Cmd(TIM1, ENABLE);
  TIM_Cmd(TIM2, ENABLE);

  /* Main Output Enable */
  TIM_CtrlPWMOutputs(TIM1, ENABLE);

  while (1)
  {}
}

方式2：输入捕获计数。TIM1 Chanel1 接至 TIM2 Channel2， TIM2 Channel2 在输入捕获中断中计数
在TIM2_IRQHandler()中加入下面代码
  if (TIM_GetITStatus(TIM2, TIM_IT_CC2) != RESET)
  { TIM_ClearITPendingBit(TIM2, TIM_IT_CC2 );
      pulseNum++;
  }

方式3：外部时钟模式2.TIM1 Channel1作为TIM3的外部时钟。
TIM_TimeBaseStructure.TIM_Period = 0xFFFF;
TIM_TimeBaseStructure.TIM_Prescaler = 0x00;
TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

TIM_ETRClockMode2Config(TIM3, TIM_ExtTRGPSC_OFF, TIM_ExtTRGPolarity_NonInverted, 0);
TIM_SetCounter(TIM3, 0);
/****************************** stm32f10x_it.c **********************************/
void TIM2_IRQHandler(void){
  if (TIM_GetITStatus(TIM2, TIM_IT_Update) != RESET)
  {
      TIM_ClearITPendingBit(TIM2, TIM_IT_Update );

      pulseNum  = TIM_GetCounter(TIM3);
      TIM_SetCounter(TIM3, 0);
      printf("\nnStep : %d,pulseNum : %d\n", nStep, pulseNum);

      TIM1->CCR1 =  ARR_Buffer[nStep] / 2;
      TIM1->ARR = ARR_Buffer[nStep];
      TIM_GenerateEvent(TIM1, TIM_EventSource_Update);

      nStep++;
      if(nStep >9)
         nStep = 0;

  }