[嵌入式]STM32F4调试编码器遇到的问题及解决（二）

上一篇文章讲到调整关键代码的位置可以解决MCU编码器对应引脚电平始终为低而导致的读不到脉冲的问题，本篇文章深入探究其背后原因。

出错时代码被放置在了void HAL_TIM_Encoder_MspInit(TIM_HandleTypeDef* tim_encoderHandle)中，而正确的时候代码则是被放置在了void MX_TIM3_Init(void)和void MX_TIM5_Init(void)函数的最后。代码是同样的代码，功能是相同的，相同的代码最终由于放置位置的差异导致了功能上的天壤之别。这就很明显地是一个顺序问题。

先来看各个代码的调用顺序，以Tim3为例。MX_TIM3_Init函数源码如下：

/* TIM3 init function */
void MX_TIM3_Init(void)
{
  TIM_Encoder_InitTypeDef sConfig = {0};
  TIM_MasterConfigTypeDef sMasterConfig = {0};

  htim3.Instance = TIM3;
  htim3.Init.Prescaler = 0;
  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
  htim3.Init.Period = 65535;
  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
  sConfig.EncoderMode = TIM_ENCODERMODE_TI12;
  sConfig.IC1Polarity = TIM_ICPOLARITY_RISING;
  sConfig.IC1Selection = TIM_ICSELECTION_DIRECTTI;
  sConfig.IC1Prescaler = TIM_ICPSC_DIV1;
  sConfig.IC1Filter = 0;
  sConfig.IC2Polarity = TIM_ICPOLARITY_FALLING;
  sConfig.IC2Selection = TIM_ICSELECTION_DIRECTTI;
  sConfig.IC2Prescaler = TIM_ICPSC_DIV1;
  sConfig.IC2Filter = 0;
  if (HAL_TIM_Encoder_Init(&htim3, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
  sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
  {
    Error_Handler();
  }
}

MX_TIM3_Init函数中调用了HAL_TIM_Encoder_Init函数，该函数在Drivers\STM32F4xx_HAL_Driver\Src\stm32f4xx_hal_tim.c中：

/**
  * @brief  Initializes the TIM Encoder Interface and initialize the associated handle.
  * @note   Switching from Center Aligned counter mode to Edge counter mode (or reverse)
  *         requires a timer reset to avoid unexpected direction
  *         due to DIR bit readonly in center aligned mode.
  *         Ex: call @ref HAL_TIM_Encoder_DeInit() before HAL_TIM_Encoder_Init()
  * @note   Encoder mode and External clock mode 2 are not compatible and must not be selected together
  *         Ex: A call for @ref HAL_TIM_Encoder_Init will erase the settings of @ref HAL_TIM_ConfigClockSource
  *         using TIM_CLOCKSOURCE_ETRMODE2 and vice versa
  * @param  htim TIM Encoder Interface handle
  * @param  sConfig TIM Encoder Interface configuration structure
  * @retval HAL status
  */
HAL_StatusTypeDef HAL_TIM_Encoder_Init(TIM_HandleTypeDef *htim,  TIM_Encoder_InitTypeDef *sConfig)
{
  uint32_t tmpsmcr;
  uint32_t tmpccmr1;
  uint32_t tmpccer;

  /* Check the TIM handle allocation */
  if (htim == NULL)
  {
    return HAL_ERROR;
  }

  /* Check the parameters */
  assert_param(IS_TIM_COUNTER_MODE(htim->Init.CounterMode));
  assert_param(IS_TIM_CLOCKDIVISION_DIV(htim->Init.ClockDivision));
  assert_param(IS_TIM_AUTORELOAD_PRELOAD(htim->Init.AutoReloadPreload));
  assert_param(IS_TIM_CC2_INSTANCE(htim->Instance));
  assert_param(IS_TIM_ENCODER_MODE(sConfig->EncoderMode));
  assert_param(IS_TIM_IC_SELECTION(sConfig->IC1Selection));
  assert_param(IS_TIM_IC_SELECTION(sConfig->IC2Selection));
  assert_param(IS_TIM_ENCODERINPUT_POLARITY(sConfig->IC1Polarity));
  assert_param(IS_TIM_ENCODERINPUT_POLARITY(sConfig->IC2Polarity));
  assert_param(IS_TIM_IC_PRESCALER(sConfig->IC1Prescaler));
  assert_param(IS_TIM_IC_PRESCALER(sConfig->IC2Prescaler));
  assert_param(IS_TIM_IC_FILTER(sConfig->IC1Filter));
  assert_param(IS_TIM_IC_FILTER(sConfig->IC2Filter));

  if (htim->State == HAL_TIM_STATE_RESET)
  {
    /* Allocate lock resource and initialize it */
    htim->Lock = HAL_UNLOCKED;

#if (USE_HAL_TIM_REGISTER_CALLBACKS == 1)
    /* Reset interrupt callbacks to legacy weak callbacks */
    TIM_ResetCallback(htim);

    if (htim->Encoder_MspInitCallback == NULL)
    {
      htim->Encoder_MspInitCallback = HAL_TIM_Encoder_MspInit;
    }
    /* Init the low level hardware : GPIO, CLOCK, NVIC */
    htim->Encoder_MspInitCallback(htim);
#else
    /* Init the low level hardware : GPIO, CLOCK, NVIC and DMA */
    HAL_TIM_Encoder_MspInit(htim);
#endif /* USE_HAL_TIM_REGISTER_CALLBACKS */
  }

  /* Set the TIM state */
  htim->State = HAL_TIM_STATE_BUSY;

  /* Reset the SMS and ECE bits */
  htim->Instance->SMCR &= ~(TIM_SMCR_SMS | TIM_SMCR_ECE);

  /* Configure the Time base in the Encoder Mode */
  TIM_Base_SetConfig(htim->Instance, &htim->Init);

  /* Get the TIMx SMCR register value */
  tmpsmcr = htim->Instance->SMCR;

  /* Get the TIMx CCMR1 register value */
  tmpccmr1 = htim->Instance->CCMR1;

  /* Get the TIMx CCER register value */
  tmpccer = htim->Instance->CCER;

  /* Set the encoder Mode */
  tmpsmcr |= sConfig->EncoderMode;

  /* Select the Capture Compare 1 and the Capture Compare 2 as input */
  tmpccmr1 &= ~(TIM_CCMR1_CC1S | TIM_CCMR1_CC2S);
  tmpccmr1 |= (sConfig->IC1Selection | (sConfig->IC2Selection << 8U));

  /* Set the Capture Compare 1 and the Capture Compare 2 prescalers and filters */
  tmpccmr1 &= ~(TIM_CCMR1_IC1PSC | TIM_CCMR1_IC2PSC);
  tmpccmr1 &= ~(TIM_CCMR1_IC1F | TIM_CCMR1_IC2F);
  tmpccmr1 |= sConfig->IC1Prescaler | (sConfig->IC2Prescaler << 8U);
  tmpccmr1 |= (sConfig->IC1Filter << 4U) | (sConfig->IC2Filter << 12U);

  /* Set the TI1 and the TI2 Polarities */
  tmpccer &= ~(TIM_CCER_CC1P | TIM_CCER_CC2P);
  tmpccer &= ~(TIM_CCER_CC1NP | TIM_CCER_CC2NP);
  tmpccer |= sConfig->IC1Polarity | (sConfig->IC2Polarity << 4U);

  /* Write to TIMx SMCR */
  htim->Instance->SMCR = tmpsmcr;

  /* Write to TIMx CCMR1 */
  htim->Instance->CCMR1 = tmpccmr1;

  /* Write to TIMx CCER */
  htim->Instance->CCER = tmpccer;

  /* Initialize the TIM state*/
  htim->State = HAL_TIM_STATE_READY;

  return HAL_OK;
}

可以看到，HAL_TIM_Encoder_Init函数中调用了HAL_TIM_Encoder_MspInit函数。这个HAL_TIM_Encoder_MspInit函数正是错误的情况下关键代码放置的位置，源码如下：

void HAL_TIM_Encoder_MspInit(TIM_HandleTypeDef* tim_encoderHandle)
{

  GPIO_InitTypeDef GPIO_InitStruct = {0};
  if(tim_encoderHandle->Instance==TIM3)
  {
  /* USER CODE BEGIN TIM3_MspInit 0 */

  /* USER CODE END TIM3_MspInit 0 */
    /* TIM3 clock enable */
    __HAL_RCC_TIM3_CLK_ENABLE();

    __HAL_RCC_GPIOA_CLK_ENABLE();
    /**TIM3 GPIO Configuration
    PA6     ------> TIM3_CH1
    PA7     ------> TIM3_CH2
    */
    GPIO_InitStruct.Pin = GPIO_PIN_6|GPIO_PIN_7;
    GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    GPIO_InitStruct.Alternate = GPIO_AF2_TIM3;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    /* TIM3 interrupt Init */
    HAL_NVIC_SetPriority(TIM3_IRQn, 0, 0);
    HAL_NVIC_EnableIRQ(TIM3_IRQn);
  /* USER CODE BEGIN TIM3_MspInit 1 */
#if 0
	//清零计数器
	__HAL_TIM_SET_COUNTER(&htim3, 0);

	//清零中断标志位
	__HAL_TIM_CLEAR_IT(&htim3, TIM_IT_UPDATE);
	//使能定时器的更新事件中断
	__HAL_TIM_ENABLE_IT(&htim3, TIM_IT_UPDATE);
	//设置更新事件请求源为：计数器溢出
	__HAL_TIM_URS_ENABLE(&htim3);

	//设置中断优先级
	HAL_NVIC_SetPriority(TIM3_IRQn, 5, 0);
	//使能定时器中断
	HAL_NVIC_EnableIRQ(TIM3_IRQn);

	//使能编码器接口
	HAL_TIM_Encoder_Start(&htim3, TIM_CHANNEL_ALL);
#endif
  /* USER CODE END TIM3_MspInit 1 */
  }
  ……
}

可以看到，如果将关键代码（上面代码中#if 0和#endif中间的内容）放在这里，则先使能了编码器接口，而后经过了HAL_TIM_Encoder_Init函数中下边的一大段初始化函数：

/* Set the TIM state */
htim->State = HAL_TIM_STATE_BUSY;

/* Reset the SMS and ECE bits */
htim->Instance->SMCR &= ~(TIM_SMCR_SMS | TIM_SMCR_ECE);

/* Configure the Time base in the Encoder Mode */
TIM_Base_SetConfig(htim->Instance, &htim->Init);

/* Get the TIMx SMCR register value */
tmpsmcr = htim->Instance->SMCR;

/* Get the TIMx CCMR1 register value */
tmpccmr1 = htim->Instance->CCMR1;

/* Get the TIMx CCER register value */
tmpccer = htim->Instance->CCER;

/* Set the encoder Mode */
tmpsmcr |= sConfig->EncoderMode;

/* Select the Capture Compare 1 and the Capture Compare 2 as input */
tmpccmr1 &= ~(TIM_CCMR1_CC1S | TIM_CCMR1_CC2S);
tmpccmr1 |= (sConfig->IC1Selection | (sConfig->IC2Selection << 8U));

/* Set the Capture Compare 1 and the Capture Compare 2 prescalers and filters */
tmpccmr1 &= ~(TIM_CCMR1_IC1PSC | TIM_CCMR1_IC2PSC);
tmpccmr1 &= ~(TIM_CCMR1_IC1F | TIM_CCMR1_IC2F);
tmpccmr1 |= sConfig->IC1Prescaler | (sConfig->IC2Prescaler << 8U);
tmpccmr1 |= (sConfig->IC1Filter << 4U) | (sConfig->IC2Filter << 12U);

/* Set the TI1 and the TI2 Polarities */
tmpccer &= ~(TIM_CCER_CC1P | TIM_CCER_CC2P);
tmpccer &= ~(TIM_CCER_CC1NP | TIM_CCER_CC2NP);
tmpccer |= sConfig->IC1Polarity | (sConfig->IC2Polarity << 4U);

/* Write to TIMx SMCR */
htim->Instance->SMCR = tmpsmcr;

/* Write to TIMx CCMR1 */
htim->Instance->CCMR1 = tmpccmr1;

/* Write to TIMx CCER */
htim->Instance->CCER = tmpccer;

/* Initialize the TIM state*/
htim->State = HAL_TIM_STATE_READY;

这段代码具体有何作用，是否会重置已经启动的编码器计数动作设置，就是这个问题的关键所在！

仔细分析一下各个代码的实际功能。

1.?HAL_TIM_Encoder_Start

HAL_TIM_Encoder_Start函数在Drivers\STM32F4xx_HAL_Driver\Src\stm32f4xx_hal_tim.c中，源码如下：

/**
  * @brief  Starts the TIM Encoder Interface.
  * @param  htim TIM Encoder Interface handle
  * @param  Channel TIM Channels to be enabled
  *          This parameter can be one of the following values:
  *            @arg TIM_CHANNEL_1: TIM Channel 1 selected
  *            @arg TIM_CHANNEL_2: TIM Channel 2 selected
  *            @arg TIM_CHANNEL_ALL: TIM Channel 1 and TIM Channel 2 are selected
  * @retval HAL status
  */
HAL_StatusTypeDef HAL_TIM_Encoder_Start(TIM_HandleTypeDef *htim, uint32_t Channel)
{
  /* Check the parameters */
  assert_param(IS_TIM_CC2_INSTANCE(htim->Instance));

  /* Enable the encoder interface channels */
  switch (Channel)
  {
    case TIM_CHANNEL_1:
    {
      TIM_CCxChannelCmd(htim->Instance, TIM_CHANNEL_1, TIM_CCx_ENABLE);
      break;
    }

    case TIM_CHANNEL_2:
    {
      TIM_CCxChannelCmd(htim->Instance, TIM_CHANNEL_2, TIM_CCx_ENABLE);
      break;
    }

    default :
    {
      TIM_CCxChannelCmd(htim->Instance, TIM_CHANNEL_1, TIM_CCx_ENABLE);
      TIM_CCxChannelCmd(htim->Instance, TIM_CHANNEL_2, TIM_CCx_ENABLE);
      break;
    }
  }
  /* Enable the Peripheral */
  __HAL_TIM_ENABLE(htim);

  /* Return function status */
  return HAL_OK;
}

1.1?TIM_CCxChannelCmd函数

同样在Drivers\STM32F4xx_HAL_Driver\Src\stm32f4xx_hal_tim.c中，源码如下：

/**
  * @brief  Enables or disables the TIM Capture Compare Channel x.
  * @param  TIMx to select the TIM peripheral
  * @param  Channel specifies the TIM Channel
  *          This parameter can be one of the following values:
  *            @arg TIM_CHANNEL_1: TIM Channel 1
  *            @arg TIM_CHANNEL_2: TIM Channel 2
  *            @arg TIM_CHANNEL_3: TIM Channel 3
  *            @arg TIM_CHANNEL_4: TIM Channel 4
  * @param  ChannelState specifies the TIM Channel CCxE bit new state.
  *          This parameter can be: TIM_CCx_ENABLE or TIM_CCx_DISABLE.
  * @retval None
  */
void TIM_CCxChannelCmd(TIM_TypeDef *TIMx, uint32_t Channel, uint32_t ChannelState)
{
  uint32_t tmp;

  /* Check the parameters */
  assert_param(IS_TIM_CC1_INSTANCE(TIMx));
  assert_param(IS_TIM_CHANNELS(Channel));

  tmp = TIM_CCER_CC1E << (Channel & 0x1FU); /* 0x1FU = 31 bits max shift */

  /* Reset the CCxE Bit */
  TIMx->CCER &= ~tmp;

  /* Set or reset the CCxE Bit */
  TIMx->CCER |= (uint32_t)(ChannelState << (Channel & 0x1FU)); /* 0x1FU = 31 bits max shift */
}

这个函数的功能是使能/禁止定时器的捕获比较通道。涉及到CCER寄存器，手册中对应的资料为：

?

1.2?__HAL_TIM_ENABLE函数

__HAL_TIM_ENABLE()在Drivers\STM32F4xx_HAL_Driver\Inc\stm32f4xx_hal_tim.h中，实际上是宏定义：

/**
  * @brief  Enable the TIM peripheral.
  * @param  __HANDLE__ TIM handle
  * @retval None
  */
#define __HAL_TIM_ENABLE(__HANDLE__)                 ((__HANDLE__)->Instance->CR1|=(TIM_CR1_CEN))

这个函数的功能是使能定时器外设。涉及到CR1寄存器，手册中对应的资料为：

?

2.??SMCR寄存器

/* Reset the SMS and ECE bits */
? htim->Instance->SMCR &= ~(TIM_SMCR_SMS | TIM_SMCR_ECE);

SMCR寄存器在手册中对应的资料为：

?

3.?TIM_Base_SetConfig

/* Configure the Time base in the Encoder Mode */
? TIM_Base_SetConfig(htim->Instance, &htim->Init);

TIM_Base_SetConfig函数同样在Drivers\STM32F4xx_HAL_Driver\Src\stm32f4xx_hal_tim.c中，源码如下：

/**
  * @brief  Time Base configuration
  * @param  TIMx TIM peripheral
  * @param  Structure TIM Base configuration structure
  * @retval None
  */
void TIM_Base_SetConfig(TIM_TypeDef *TIMx, TIM_Base_InitTypeDef *Structure)
{
  uint32_t tmpcr1;
  tmpcr1 = TIMx->CR1;

  /* Set TIM Time Base Unit parameters ---------------------------------------*/
  if (IS_TIM_COUNTER_MODE_SELECT_INSTANCE(TIMx))
  {
    /* Select the Counter Mode */
    tmpcr1 &= ~(TIM_CR1_DIR | TIM_CR1_CMS);
    tmpcr1 |= Structure->CounterMode;
  }

  if (IS_TIM_CLOCK_DIVISION_INSTANCE(TIMx))
  {
    /* Set the clock division */
    tmpcr1 &= ~TIM_CR1_CKD;
    tmpcr1 |= (uint32_t)Structure->ClockDivision;
  }

  /* Set the auto-reload preload */
  MODIFY_REG(tmpcr1, TIM_CR1_ARPE, Structure->AutoReloadPreload);

  TIMx->CR1 = tmpcr1;

  /* Set the Autoreload value */
  TIMx->ARR = (uint32_t)Structure->Period ;

  /* Set the Prescaler value */
  TIMx->PSC = Structure->Prescaler;

  if (IS_TIM_REPETITION_COUNTER_INSTANCE(TIMx))
  {
    /* Set the Repetition Counter value */
    TIMx->RCR = Structure->RepetitionCounter;
  }

  /* Generate an update event to reload the Prescaler
     and the repetition counter (only for advanced timer) value immediately */
  TIMx->EGR = TIM_EGR_UG;
}

3.1??IS_TIM_COUNTER_MODE_SELECT_INSTANCE

IS_TIM_COUNTER_MODE_SELECT_INSTANCE宏定义在Drivers\CMSIS\Device\ST\STM32F4xx\Include\stm32f405xx.h中：

/****************** TIM Instances : supporting counting mode selection ********/
#define IS_TIM_COUNTER_MODE_SELECT_INSTANCE(INSTANCE)  (((INSTANCE) == TIM1) || \
                                                        ((INSTANCE) == TIM2) || \
                                                        ((INSTANCE) == TIM3) || \
                                                        ((INSTANCE) == TIM4) || \
                                                        ((INSTANCE) == TIM5) || \
                                                        ((INSTANCE) == TIM8))

3.2?IS_TIM_CLOCK_DIVISION_INSTANCE宏定义同样在Drivers\CMSIS\Device\ST\STM32F4xx\Include\stm32f405xx.h中：

/****************** TIM Instances : supporting clock division *****************/
#define IS_TIM_CLOCK_DIVISION_INSTANCE(INSTANCE) (((INSTANCE) == TIM1)  || \
                                                  ((INSTANCE) == TIM2) || \
                                                  ((INSTANCE) == TIM3) || \
                                                  ((INSTANCE) == TIM4) || \
                                                  ((INSTANCE) == TIM5) || \
                                                  ((INSTANCE) == TIM8) || \
                                                  ((INSTANCE) == TIM9) || \
                                                  ((INSTANCE) == TIM10)|| \
                                                  ((INSTANCE) == TIM11)|| \
                                                  ((INSTANCE) == TIM12)|| \
                                                  ((INSTANCE) == TIM13)|| \
                                                  ((INSTANCE) == TIM14))