设置 TIM3_CH2 的 PWM 模式，使能 TIM3 的 CH2 输出

/**
  ******************************************************************************
  * @file    stm32f10x_tim.h
  * @author  MCD Application Team
  * @version V3.5.0
  * @date    11-March-2011
  * @brief   This file contains all the functions prototypes for the TIM firmware 
  *          library.
  ******************************************************************************
  * @attention
  *
  * THE PRESENT FIRMWARE WHICH IS FOR GUIDANCE ONLY AIMS AT PROVIDING CUSTOMERS
  * WITH CODING INFORMATION REGARDING THEIR PRODUCTS IN ORDER FOR THEM TO SAVE
  * TIME. AS A RESULT, STMICROELECTRONICS SHALL NOT BE HELD LIABLE FOR ANY
  * DIRECT, INDIRECT OR CONSEQUENTIAL DAMAGES WITH RESPECT TO ANY CLAIMS ARISING
  * FROM THE CONTENT OF SUCH FIRMWARE AND/OR THE USE MADE BY CUSTOMERS OF THE
  * CODING INFORMATION CONTAINED HEREIN IN CONNECTION WITH THEIR PRODUCTS.
  *
  * <h2><center>&copy; COPYRIGHT 2011 STMicroelectronics</center></h2>
  ******************************************************************************
  */


/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __STM32F10x_TIM_H
#define __STM32F10x_TIM_H


#ifdef __cplusplus
 extern "C" {
#endif


/* Includes ------------------------------------------------------------------*/
#include "stm32f10x.h"


/** @addtogroup STM32F10x_StdPeriph_Driver
  * @{
  */


/** @addtogroup TIM
  * @{
  */ 


/** @defgroup TIM_Exported_Types
  * @{
  */ 


/** 
  * @brief  TIM Time Base Init structure definition
  * @note   This structure is used with all TIMx except for TIM6 and TIM7.    
  */


typedef struct
{
  uint16_t TIM_Prescaler;         /*!< Specifies the prescaler value used to divide the TIM clock.
                                       This parameter can be a number between 0x0000 and 0xFFFF */


  uint16_t TIM_CounterMode;       /*!< Specifies the counter mode.
                                       This parameter can be a value of @ref TIM_Counter_Mode */


  uint16_t TIM_Period;            /*!< Specifies the period value to be loaded into the active
                                       Auto-Reload Register at the next update event.
                                       This parameter must be a number between 0x0000 and 0xFFFF.  */ 


  uint16_t TIM_ClockDivision;     /*!< Specifies the clock division.
                                      This parameter can be a value of @ref TIM_Clock_Division_CKD */


  uint8_t TIM_RepetitionCounter;  /*!< Specifies the repetition counter value. Each time the RCR downcounter
                                       reaches zero, an update event is generated and counting restarts
                                       from the RCR value (N).
                                       This means in PWM mode that (N+1) corresponds to:
                                          - the number of PWM periods in edge-aligned mode
                                          - the number of half PWM period in center-aligned mode
                                       This parameter must be a number between 0x00 and 0xFF. 
                                       @note This parameter is valid only for TIM1 and TIM8. */
} TIM_TimeBaseInitTypeDef;