时钟控制AD采样的问题

只看该作者 · 2009-4-22 13:58

对一有刷马达进行控制(控制周期为100Hz)，PWM频率为10KHz(TIM_Period=1800)，希望能在PWM开通的中间位置对马达的电流采样 (因为电路设计

的缘故，PWM关断时ADC的输入被嵌位在3V)；
例如：如果TIM_Pulse=600，那么希望在计数器等于300时采样
程序中选择时钟2的第四通道控制PWM输出，选择时钟2的第二通道控制AD采样
相关代码如下，只用速度环控制，马达运行正常，但ADC采样点落在PWM关断期间，因为ADC值对应的总是3V左右
大家帮忙看看是那里出了问题，先谢谢各位了。

void  PWMInitialization(void)
  {

  /*初始化PWM输出管脚*/
  GPIO_InitStructure.GPIO_Pin =  MOTOR_PWM_PIN;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_Init(MOTOR_PWM_PORT, &GPIO_InitStructure);
  /* 选择时钟2的第四通道控制PWM输出 */
  TIM_TimeBaseStructure.TIM_Period = 1800;      //频率为10KHz
  TIM_TimeBaseStructure.TIM_Prescaler = 0x00;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 0;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OC4Init(TIM2, &TIM_OCInitStructure);
  TIM_OC4PreloadConfig(TIM2, TIM_OCPreload_Disable);
  TIM_ARRPreloadConfig(TIM2, ENABLE);
  TIM_Cmd(TIM2, ENABLE);

  /* 选择时钟2的第二通道控制AD采样 */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Timing;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 0;
  TIM_OC2Init(TIM2, &TIM_OCInitStructure);
  TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Disable);
  TIM_ARRPreloadConfig(TIM2, ENABLE);

  /*允许时钟的相关中断*/
  NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQChannel;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);
  TIM_ITConfig(TIM2, TIM_IT_Update|TIM_IT_CC2, ENABLE);
}

void MotorControl(void)   // 频率为100Hz
{
  .........
  //控制算法计算PWM控制量，并存在MotorPWMValue中
  .........
    TIM_OCInitStructure.TIM_Pulse = MotorPWMValue;
  .........
}


void TIM2_IRQHandler(void)  //频率为10KHz
{
    u16 capture;

    if (TIM_GetITStatus(TIM2, TIM_IT_Update) == SET)
    {
    capture = TIM_GetCapture1((TIM2);
    TIM_ClearITPendingBit(TIM2, TIM_IT_Update|TIM_IT_CC2);
    //TIM_SetCompare2(TIM2, MotorPWMValue/2);
    TIM_SetCompare2(TIM2, capture+MotorPWMValue/2);
    }

    if (TIM_GetITStatus(TIM2, TIM_IT_CC2) == SET)
    {
    TIM_ClearITPendingBit(TIM2, TIM_IT_Update|TIM_IT_CC2);
    GetADCResult(MotorCurrent);
    }
}