STM32的TIM2触发ADC问题，版主和各位朋友帮忙

只看该作者 · 2011-10-20 21:31

我使用TIM2的TIM_TRGOSource_OC2Ref来触发ADC转换，按照我的理解我改变OC2比较寄存器的值就可以控制ADC开始转换的时间，但是实验结果是ADC总在OC2计数器复位后开始。如下图：

只看该作者 · 2011-10-20 21:37

附上TIM2初始化代码，10KHz，占空比25%，即OC2Ref，我在PA1引脚输出了OC2的波形，好示波器做抓取比较

void Init_T2(void)
{
TIM_OCInitTypeDef  TIM_OCInitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

GPIO_InitTypeDef GPIOA_InitStruct;

GPIOA_InitStruct.GPIO_Pin = GPIO_Pin_1;
GPIOA_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;
GPIOA_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(GPIOA, &GPIOA_InitStruct);

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE );

  TIM_DeInit(TIM2);
  TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
  TIM_TimeBaseStructure.TIM_Prescaler = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = (SystemCoreClock / 10000 ) - 1;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

  TIM_OCStructInit(&TIM_OCInitStructure);

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
  TIM_OCInitStructure.TIM_Pulse = 1800;
  TIM_OC2Init(TIM2, &TIM_OCInitStructure);

TIM_SelectMasterSlaveMode(TIM2, TIM_MasterSlaveMode_Enable);
TIM_SelectOutputTrigger(TIM2, TIM_TRGOSource_OC2Ref);
  /* TIM1 counter enable */
  TIM_Cmd(TIM2, ENABLE);

  /* TIM1 Main Output Enable */
  TIM_CtrlPWMOutputs(TIM2, ENABLE);

}

只看该作者 · 2011-10-20 21:41

ADC初始化代码如下，3路AD。使用TIM2的OC2ref触发ADC转换，转换完成后触发DMA中断：
void ADC_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;
  DMA_InitTypeDef DMA_InitStructure;
  ADC_InitTypeDef  ADC_InitStructure;

  /* Configure PC.00, PC.02 and PC.03 (ADC Channel10, Channel12 and Channel13)*/
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0 | GPIO_Pin_2 | GPIO_Pin_3;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AIN;
  GPIO_Init(GPIOC, &GPIO_InitStructure);

  /* init ADC clock */
  RCC_ADCCLKConfig(RCC_PCLK2_Div6); /* 72MHz/6 */
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1 , ENABLE );

  /* DMA1 channel1 configuration ----------------------------------------------*/
  DMA_DeInit(DMA1_Channel1);
  DMA_InitStructure.DMA_PeripheralBaseAddr = ADC1_DR_Address;
  DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&ADCConvertedValue;
  DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
  DMA_InitStructure.DMA_BufferSize = 3;
  DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
  DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
  DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
  DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
  DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
  DMA_InitStructure.DMA_Priority = DMA_Priority_High;
  DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
  DMA_Init(DMA1_Channel1, &DMA_InitStructure);
  /* Enable DMA1 channel1 */
  DMA_Cmd(DMA1_Channel1, ENABLE);

  /* ADC1 configuration ------------------------------------------------------*/
  ADC_InitStructure.ADC_Mode = ADC_Mode_Independent;
  ADC_InitStructure.ADC_ScanConvMode = ENABLE;
  ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
  ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T2_CC2;
  ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Right;
  ADC_InitStructure.ADC_NbrOfChannel = ADC_NUM;
  ADC_Init(ADC1, &ADC_InitStructure);

  /* ADC1 regular configuration */
  ADC_RegularChannelConfig(ADC1, ADC_Channel_10, 1, ADC_SampleTime_1Cycles5);
  ADC_RegularChannelConfig(ADC1, ADC_Channel_12, 2, ADC_SampleTime_1Cycles5);
  ADC_RegularChannelConfig(ADC1, ADC_Channel_13, 3, ADC_SampleTime_1Cycles5);

ADC_DMACmd(ADC1 , ENABLE);
ADC_ExternalTrigConvCmd(ADC1, ENABLE);


ADC_Cmd(ADC1 , ENABLE);
ADC_ResetCalibration(ADC1);
while(ADC_GetResetCalibrationStatus(ADC1)){};
ADC_StartCalibration(ADC1);
while(ADC_GetCalibrationStatus(ADC1)){};

DMA_ITConfig(DMA1_Channel1, DMA_IT_TC, ENABLE);
}

1万 · 2011-10-21 08:49

不能直接提供你的功能，不过你可以让 CC2 输出反相，再变换 CCR2 的值来实现。

只看该作者 · 2011-10-21 09:37

楼主你漏掉看规格书里面说的一句话：“When an external trigger is selected for ADC regular or injected conversion, only the rising edge of the signal can start the conversion.” 这里你只要将PWM模式换成PWM2即可。但是波形跟你想要的正好是反向互补。这样你还是控制CCR2就可以控制ADC转换的时刻。波形应该对你意义不大吧！