PWM 输入模式 

此模式是输入捕获模式的一个特例。其实现步骤与输入捕获模式基本相同，仅存在以下不同之处：
 
例如，可通过以下步骤对应用于 TI1① 的 PWM 的周期（位于 TIMx_CCR1⑨ 寄存器中）和占空 比（位于 TIMx_CCR2⑮ 寄存器中）进行测量（取决于 CK_INT① 频率和预分频器的值）： 
● IC1⑦ 与 IC2⑬ 两个信号被映射至同一个 TI1① 输入。 
● IC1⑦ 与 IC2⑬ 这两个信号在边沿处有效，但极性相反。 
● 选择TI1FP 与 TI2FP 中的 TI1FP④ 信号作为触发输入(也可选择TI2FP)，并将从模式控制器配置为复位模式。 
● 向 TIMx_CCMR1 寄存器中的 CC1S② 位写入 01,选择 TIMx_CCR1 的有效输入： TI1①。 
● 向 CC1P 位和 CC1NP③ 位写入 “0” （上升沿有效）。选择 TI1FP1④ 的有效极性 : 上升沿有效（用于 TIMx_CCR1⑨ 中捕获上升沿时的计数值 和 TIMx_CNT⑯ 计数器清零）： 
● 向 TIMx_CCMR1 寄存器中的 CC2S⑪ 位写入 10,选择 TIMx_CCR2 的有效输入： TI1①。 
● 向 CC2P 位和 CC2NP⑫ 位写入 “1” （下降沿有效）。选择 TI1FP2 的有效极性 : 下降沿有效（用于 TIMx_CCR2⑮ 中捕获下降沿时的计数值）。 
● 选择有效触发输入：向 TIMx_SMCR 寄存器中的 TS⑤ 位写入 101（选择 TI1FP1）。 
● 向 TIMx_SMCR 寄存器中的 SMS⑥ 位写入 100 , 将从模式控制器配置为复位模式。 
● 向 TIMx_CCER 寄存器中的 CC1E⑧ 位和 CC2E⑭ 位写入“1” , 使能捕获。 
根据F103的库函数TIM_PWMIConfig()微调了数据手册中框图的位置关系.

TIM_PWMIConfig（）函数

/*	stm32f10x_tim.h 中宏定义 */
#define  TIM_ICPolarity_Rising             ((uint16_t)0x0000)
#define  TIM_ICPolarity_Falling            ((uint16_t)0x0002)

#define TIM_ICSelection_DirectTI           ((uint16_t)0x0001) /*!< TIM Input 1, 2, 3 or 4 is selected to be connected to IC1, IC2, IC3 or IC4, respectively */
#define TIM_ICSelection_IndirectTI         ((uint16_t)0x0002) /*!< TIM Input 1, 2, 3 or 4 is selected to be connected to IC2, IC1, IC4 or IC3, respectively. */



/*	stm32f10x_tim.c 中PWMIConfig定义 */
/**
 * @brief  Configures the TIM peripheral according to the specified
 *         parameters in the TIM_ICInitStruct to measure an external PWM signal.
 * @param  TIMx: where x can be  1, 2, 3, 4, 5, 8, 9, 12 or 15 to select the TIM peripheral.
 * @param  TIM_ICInitStruct: pointer to a TIM_ICInitTypeDef structure
 *         that contains the configuration information for the specified TIM peripheral.
 * @retval None
 */
void TIM_PWMIConfig(TIM_TypeDef *TIMx, TIM_ICInitTypeDef *TIM_ICInitStruct)
{
    uint16_t icoppositepolarity = TIM_ICPolarity_Rising;
    uint16_t icoppositeselection = TIM_ICSelection_DirectTI;
    /* Check the parameters */
    assert_param(IS_TIM_LIST6_PERIPH(TIMx));
	
	/*互补极性设置*/
    /* Select the Opposite Input Polarity */
    if (TIM_ICInitStruct->TIM_ICPolarity == TIM_ICPolarity_Rising)
    {
        icoppositepolarity = TIM_ICPolarity_Falling;
    }
    else
    {
        icoppositepolarity = TIM_ICPolarity_Rising;
    }

    /*交叉通道设置*/
	/* Select the Opposite Input */
    if (TIM_ICInitStruct->TIM_ICSelection == TIM_ICSelection_DirectTI)
    {
        icoppositeselection = TIM_ICSelection_IndirectTI;
    }
    else
    {
        icoppositeselection = TIM_ICSelection_DirectTI;
    }

	/*分别配置IC1,IC2通道*/
    if (TIM_ICInitStruct->TIM_Channel == TIM_Channel_1)
    {
        /* TI1 Configuration */
        TI1_Config(TIMx, TIM_ICInitStruct->TIM_ICPolarity, TIM_ICInitStruct->TIM_ICSelection,
                   TIM_ICInitStruct->TIM_ICFilter);
        /* Set the Input Capture Prescaler value */
        TIM_SetIC1Prescaler(TIMx, TIM_ICInitStruct->TIM_ICPrescaler);
        /* TI2 Configuration */
        TI2_Config(TIMx, icoppositepolarity, icoppositeselection, TIM_ICInitStruct->TIM_ICFilter);
        /* Set the Input Capture Prescaler value */
        TIM_SetIC2Prescaler(TIMx, TIM_ICInitStruct->TIM_ICPrescaler);
    }
    else
    {
        /* TI2 Configuration */
        TI2_Config(TIMx, TIM_ICInitStruct->TIM_ICPolarity, TIM_ICInitStruct->TIM_ICSelection,
                   TIM_ICInitStruct->TIM_ICFilter);
        /* Set the Input Capture Prescaler value */
        TIM_SetIC2Prescaler(TIMx, TIM_ICInitStruct->TIM_ICPrescaler);
        /* TI1 Configuration */
        TI1_Config(TIMx, icoppositepolarity, icoppositeselection, TIM_ICInitStruct->TIM_ICFilter);
        /* Set the Input Capture Prescaler value */
        TIM_SetIC1Prescaler(TIMx, TIM_ICInitStruct->TIM_ICPrescaler);
    }
}

TI1_Config （函数）

/*	通道 1 配置*/
/**
 * @brief  Configure the TI1 as Input.
 * @param  TIMx: where x can be 1 to 17 except 6 and 7 to select the TIM peripheral.
 * @param  TIM_ICPolarity : The Input Polarity.
 *   This parameter can be one of the following values:
 *     @arg TIM_ICPolarity_Rising
 *     @arg TIM_ICPolarity_Falling
 * @param  TIM_ICSelection: specifies the input to be used.
 *   This parameter can be one of the following values:
 *     @arg TIM_ICSelection_DirectTI: TIM Input 1 is selected to be connected to IC1.
 *     @arg TIM_ICSelection_IndirectTI: TIM Input 1 is selected to be connected to IC2.
 *     @arg TIM_ICSelection_TRC: TIM Input 1 is selected to be connected to TRC.
 * @param  TIM_ICFilter: Specifies the Input Capture Filter.
 *   This parameter must be a value between 0x00 and 0x0F.
 * @retval None
 */
static void TI1_Config(TIM_TypeDef *TIMx, uint16_t TIM_ICPolarity, uint16_t TIM_ICSelection,
                       uint16_t TIM_ICFilter)
{
    uint16_t tmpccmr1 = 0, tmpccer = 0;
    /* Disable the Channel 1: Reset the CC1E Bit */
    TIMx->CCER &= (uint16_t) ~((uint16_t)TIM_CCER_CC1E);
    tmpccmr1 = TIMx->CCMR1;
    tmpccer = TIMx->CCER;
    /* Select the Input and set the filter */
    tmpccmr1 &= (uint16_t)(((uint16_t) ~((uint16_t)TIM_CCMR1_CC1S)) & ((uint16_t) ~((uint16_t)TIM_CCMR1_IC1F)));
    tmpccmr1 |= (uint16_t)(TIM_ICSelection | (uint16_t)(TIM_ICFilter << (uint16_t)4));

    if ((TIMx == TIM1) || (TIMx == TIM8) || (TIMx == TIM2) || (TIMx == TIM3) ||
        (TIMx == TIM4) || (TIMx == TIM5))
    {
        /* Select the Polarity and set the CC1E Bit */
        tmpccer &= (uint16_t) ~((uint16_t)(TIM_CCER_CC1P));
        tmpccer |= (uint16_t)(TIM_ICPolarity | (uint16_t)TIM_CCER_CC1E);
    }
    else
    {
        /* Select the Polarity and set the CC1E Bit */
        tmpccer &= (uint16_t) ~((uint16_t)(TIM_CCER_CC1P | TIM_CCER_CC1NP));
        tmpccer |= (uint16_t)(TIM_ICPolarity | (uint16_t)TIM_CCER_CC1E);
    }

    /* Write to TIMx CCMR1 and CCER registers */
    TIMx->CCMR1 = tmpccmr1;
    TIMx->CCER = tmpccer;
}

TI2_Config （函数）

/*	通道2配置*/
/**
 * @brief  Configure the TI2 as Input.
 * @param  TIMx: where x can be 1, 2, 3, 4, 5, 8, 9, 12 or 15 to select the TIM peripheral.
 * @param  TIM_ICPolarity : The Input Polarity.
 *   This parameter can be one of the following values:
 *     @arg TIM_ICPolarity_Rising
 *     @arg TIM_ICPolarity_Falling
 * @param  TIM_ICSelection: specifies the input to be used.
 *   This parameter can be one of the following values:
 *     @arg TIM_ICSelection_DirectTI: TIM Input 2 is selected to be connected to IC2.
 *     @arg TIM_ICSelection_IndirectTI: TIM Input 2 is selected to be connected to IC1.
 *     @arg TIM_ICSelection_TRC: TIM Input 2 is selected to be connected to TRC.
 * @param  TIM_ICFilter: Specifies the Input Capture Filter.
 *   This parameter must be a value between 0x00 and 0x0F.
 * @retval None
 */
static void TI2_Config(TIM_TypeDef *TIMx, uint16_t TIM_ICPolarity, uint16_t TIM_ICSelection,
                       uint16_t TIM_ICFilter)
{
    uint16_t tmpccmr1 = 0, tmpccer = 0, tmp = 0;
    /* Disable the Channel 2: Reset the CC2E Bit */
    TIMx->CCER &= (uint16_t) ~((uint16_t)TIM_CCER_CC2E);
    tmpccmr1 = TIMx->CCMR1;
    tmpccer = TIMx->CCER;
    tmp = (uint16_t)(TIM_ICPolarity << 4);
    /* Select the Input and set the filter */
    tmpccmr1 &= (uint16_t)(((uint16_t) ~((uint16_t)TIM_CCMR1_CC2S)) & ((uint16_t) ~((uint16_t)TIM_CCMR1_IC2F)));
    tmpccmr1 |= (uint16_t)(TIM_ICFilter << 12);
    tmpccmr1 |= (uint16_t)(TIM_ICSelection << 8);

    if ((TIMx == TIM1) || (TIMx == TIM8) || (TIMx == TIM2) || (TIMx == TIM3) ||
        (TIMx == TIM4) || (TIMx == TIM5))
    {
        /* Select the Polarity and set the CC2E Bit */
        tmpccer &= (uint16_t) ~((uint16_t)(TIM_CCER_CC2P));
        tmpccer |= (uint16_t)(tmp | (uint16_t)TIM_CCER_CC2E);
    }
    else
    {
        /* Select the Polarity and set the CC2E Bit */
        tmpccer &= (uint16_t) ~((uint16_t)(TIM_CCER_CC2P | TIM_CCER_CC2NP));
        tmpccer |= (uint16_t)(TIM_ICPolarity | (uint16_t)TIM_CCER_CC2E);
    }

    /* Write to TIMx CCMR1 and CCER registers */
    TIMx->CCMR1 = tmpccmr1;
    TIMx->CCER = tmpccer;
}