STM32 USB学习笔记4

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主机环境：Windows 7 SP1

开发环境：MDK5.14

目标板：STM32F103C8T6

开发库：STM32F1Cube库和STM32_USB_Device_Library

前面分析了USB的描述符文件，现在分析一下usbd_conf文件，usbd_conf.h文件是配置文件，如下：

/* Define to prevent recursive inclusion -------------------------------------*/#ifndef __USBD_CONF_H#define __USBD_CONF_H/* Includes ------------------------------------------------------------------*/#include "stm32f1xx_hal.h"#include <stdio.h>#include <stdlib.h>#include <string.h>/* Exported types ------------------------------------------------------------*//* Exported constants --------------------------------------------------------*//* Common Config */#define USBD_MAX_NUM_INTERFACES               1#define USBD_MAX_NUM_CONFIGURATION            1#define USBD_MAX_STR_DESC_SIZ                 0x100#define USBD_SUPPORT_USER_STRING              0#define USBD_SELF_POWERED                     1#define USBD_DEBUG_LEVEL                      0/* Exported macro ------------------------------------------------------------*//* Memory management macros *//* For footprint reasons and since only one allocation is handled in the CDC class   driver, the malloc/free is changed into a static allocation method */void *USBD_static_malloc(uint32_t size);void USBD_static_free(void *p);#define MAX_STATIC_ALLOC_SIZE     140 /* CDC Class Driver Structure size */#define USBD_malloc               (uint32_t *)USBD_static_malloc#define USBD_free                 USBD_static_free#define USBD_memset               /* Not used */#define USBD_memcpy               /* Not used *//* DEBUG macros */#if (USBD_DEBUG_LEVEL > 0)#define  USBD_UsrLog(...)   printf(__VA_ARGS__);\                            printf("\n");#else#define USBD_UsrLog(...)#endif#if (USBD_DEBUG_LEVEL > 1)#define  USBD_ErrLog(...)   printf("ERROR: ") ;\                            printf(__VA_ARGS__);\                            printf("\n");#else#define USBD_ErrLog(...)#endif#if (USBD_DEBUG_LEVEL > 2)#define  USBD_DbgLog(...)   printf("DEBUG : ") ;\                            printf(__VA_ARGS__);\                            printf("\n");#else#define USBD_DbgLog(...)#endif/* Exported functions ------------------------------------------------------- */#endif /* __USBD_CONF_H */

配置文件很简单，指明最大接口数为1，最大配置数为1，不支持用户字符串，支持自供电，调试级别为0，在USB通信中USB设备支持两种供电方式：自供电(设备有自己独立电源)，总线供电(设备由USB主机提供电源)。同时，在这里采用静态空间分配方案，分配的静态空间大小为140字节。调试界别为0是没有调试信息输出的，根据自己需求来使能调试功能。usbd_conf.c文件要复杂一些，用于实现USB设备库的回调函数以及MCU的一些底层初始化。各个中断的服务例程在stm32f1xx_it.c文件中，如下：

void SysTick_Handler(void){  Toggle_Leds();  HAL_IncTick();}/******************************************************************************//*                 STM32F1xx Peripherals Interrupt Handlers                   *//*  Add here the Interrupt Handler for the used peripheral(s) (PPP), for the  *//*  available peripheral interrupt handler's name please refer to the startup *//*  file (startup_stm32f1xx.s).                                               *//******************************************************************************//**  * @brief  This function handles USB Handler.  * @param  None  * @retval None  */void USB_LP_CAN1_RX0_IRQHandler(void){  HAL_PCD_IRQHandler(&hpcd);}/**  * @brief  This function handles DMA interrupt request.  * @param  None  * @retval None  */void USARTx_DMA_TX_IRQHandler(void){  HAL_DMA_IRQHandler(UartHandle.hdmatx);}/**  * @brief  This function handles UART interrupt request.    * @param  None  * @retval None  */void USARTx_IRQHandler(void){  HAL_UART_IRQHandler(&UartHandle);}/**  * @brief  This function handles TIM interrupt request.  * @param  None  * @retval None  */void TIMx_IRQHandler(void){  HAL_TIM_IRQHandler(&TimHandle);}

中断服务例程很简单提供了一个IRQHandler接口，通过该接口会调用一些回调函数来实现具体的处理，其中各个接口可以在库函数说明中找到，如下：

USB底层API如下：

以上这些接口是需要在usbd_conf.c文件中实现的，此外还有一个USB接口的硬件IO初始化，如下：

/**  * @brief  Initializes the PCD MSP.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_MspInit(PCD_HandleTypeDef *hpcd){  GPIO_InitTypeDef  GPIO_InitStruct;     /* Enable the GPIOA clock */  __HAL_RCC_GPIOA_CLK_ENABLE();    /* Configure USB DM/DP pins */  GPIO_InitStruct.Pin = (GPIO_PIN_11 | GPIO_PIN_12);  GPIO_InitStruct.Mode = GPIO_MODE_AF_INPUT;  GPIO_InitStruct.Pull = GPIO_PULLUP;  GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);    /* Enable USB Clock */  __HAL_RCC_USB_CLK_ENABLE();      /* Set USB Interrupt priority */  HAL_NVIC_SetPriority(USB_LP_CAN1_RX0_IRQn, 7, 0);  /* Enable USB Interrupt */  HAL_NVIC_EnableIRQ(USB_LP_CAN1_RX0_IRQn);}/**  * @brief  De-Initializes the PCD MSP.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_MspDeInit(PCD_HandleTypeDef *hpcd){  /* Disable USB FS Clock */  __HAL_RCC_USB_CLK_DISABLE();}

设置USB的硬件IO口为复用模式，并设置中断优先级且使能USB中断，USB中断号有三个：USB低优先级中断(20)，USB高优先级中断(19)，USB唤醒中断(42)，这里是使能的USB低优先级中断，所有的USB事件均可触发该中断。USB底层回调函数接口实现如下：

/*******************************************************************************                       LL Driver Callbacks (PCD -> USB Device Library)*******************************************************************************//**  * @brief  SetupStage callback.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_SetupStageCallback(PCD_HandleTypeDef *hpcd){  USBD_LL_SetupStage((USBD_HandleTypeDef*)hpcd->pData, (uint8_t *)hpcd->Setup);}/**  * @brief  DataOut Stage callback.  * @param  hpcd: PCD handle  * @param  epnum: Endpoint Number  * @retval None  */void HAL_PCD_DataOutStageCallback(PCD_HandleTypeDef *hpcd, uint8_t epnum){  USBD_LL_DataOutStage((USBD_HandleTypeDef*)hpcd->pData, epnum, hpcd->OUT_ep[epnum].xfer_buff);}/**  * @brief  DataIn Stage callback.  * @param  hpcd: PCD handle  * @param  epnum: Endpoint Number  * @retval None  */void HAL_PCD_DataInStageCallback(PCD_HandleTypeDef *hpcd, uint8_t epnum){  USBD_LL_DataInStage((USBD_HandleTypeDef*)hpcd->pData, epnum, hpcd->IN_ep[epnum].xfer_buff);}/**  * @brief  SOF callback.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_SOFCallback(PCD_HandleTypeDef *hpcd){  USBD_LL_SOF((USBD_HandleTypeDef*)hpcd->pData);}/**  * @brief  Reset callback.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_ResetCallback(PCD_HandleTypeDef *hpcd){  USBD_LL_SetSpeed((USBD_HandleTypeDef*)hpcd->pData, USBD_SPEED_FULL);  /* Reset Device */  USBD_LL_Reset((USBD_HandleTypeDef*)hpcd->pData);}/**  * @brief  Suspend callback.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_SuspendCallback(PCD_HandleTypeDef *hpcd){  /* Inform USB library that core enters in suspend Mode */  USBD_LL_Suspend((USBD_HandleTypeDef*)hpcd->pData);}/**  * @brief  Resume callback.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_ResumeCallback(PCD_HandleTypeDef *hpcd){  USBD_LL_Resume((USBD_HandleTypeDef*)hpcd->pData);}/**  * @brief  ISOOUTIncomplete callback.  * @param  hpcd: PCD handle  * @param  epnum: Endpoint Number  * @retval None  */void HAL_PCD_ISOOUTIncompleteCallback(PCD_HandleTypeDef *hpcd, uint8_t epnum){  USBD_LL_IsoOUTIncomplete((USBD_HandleTypeDef*)hpcd->pData, epnum);}/**  * @brief  ISOINIncomplete callback.  * @param  hpcd: PCD handle  * @param  epnum: Endpoint Number  * @retval None  */void HAL_PCD_ISOINIncompleteCallback(PCD_HandleTypeDef *hpcd, uint8_t epnum){  USBD_LL_IsoINIncomplete((USBD_HandleTypeDef*)hpcd->pData, epnum);}/**  * @brief  ConnectCallback callback.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_ConnectCallback(PCD_HandleTypeDef *hpcd){  USBD_LL_DevConnected((USBD_HandleTypeDef*)hpcd->pData);}/**  * @brief  Disconnect callback.  * @param  hpcd: PCD handle  * @retval None  */void HAL_PCD_DisconnectCallback(PCD_HandleTypeDef *hpcd){  USBD_LL_DevDisconnected((USBD_HandleTypeDef*)hpcd->pData);}

每一个回调函数都是调用的usbd_core.c中的底层函数，对于不同的USB类该回调函数的接口实现是类似的，分别对应了触发USB中断的各个情况，跟串口中断不同，串口中断我们一般关心接收和发送中断即可。而USB的中断源比较多，从回调函数的个数就可以看得出来，即使这样，但这些回调函数里面有几个是为空的，如同步传输完成的回调函数以及设备连接的回调函数，此外，HAL_PCD_IRQHandler()里是没有调用同步传输完成回调函数的，在OTG模块的中断服务例程里才有调用。既然在全速模式下回调函数为空就不必刻意关注该回调函数了。重点关注Setup、DataIn、DataOut等即可，与之相关的是USB通信中的Setup阶段、数据阶段，所有的USB通信请求都是由USB主机发起，一般分为三个阶段：设置阶段、数据阶段、状态阶段。其中数据阶段是可以省略的。具体内容在后面遇到再分析，至此，USB中断底层回调函数浏览完毕，还剩下底层的设备驱动API，在分析之前需要注意两个个重要的结构体PCD_HandleTypeDef和USBD_HandleTypeDef，前者是STM32Cube库提供的跟寄存器相关的数据结构，后者是USB器件库提供的跟USB协议相关的数据结构，在例程中两者相互引用，PCD_HandleTypeDef结构如下：

/**   * @brief  PCD Handle Structure definition  */typedef struct{  PCD_TypeDef             *Instance;   /*!< Register base address               */  PCD_InitTypeDef         Init;        /*!< PCD required parameters             */  __IO uint8_t            USB_Address; /*!< USB Address: not used by USB OTG FS */    PCD_EPTypeDef           IN_ep[15];   /*!< IN endpoint parameters              */  PCD_EPTypeDef           OUT_ep[15];  /*!< OUT endpoint parameters             */  HAL_LockTypeDef         Lock;        /*!< PCD peripheral status               */  __IO PCD_StateTypeDef   State;       /*!< PCD communication state             */  uint32_t                Setup[12];   /*!< Setup packet buffer                 */  void                    *pData;      /*!< Pointer to upper stack Handler      */} PCD_HandleTypeDef;/**  * @brief  PCD State structure definition  */typedef enum{  HAL_PCD_STATE_RESET   = 0x00,  HAL_PCD_STATE_READY   = 0x01,  HAL_PCD_STATE_ERROR   = 0x02,  HAL_PCD_STATE_BUSY    = 0x03,  HAL_PCD_STATE_TIMEOUT = 0x04} PCD_StateTypeDef;#if defined (USB)typedef USB_TypeDef        PCD_TypeDef;typedef USB_CfgTypeDef     PCD_InitTypeDef;typedef USB_EPTypeDef      PCD_EPTypeDef;#endif /* USB *//**   * @brief Universal Serial Bus Full Speed Device  */  typedef struct{  __IO uint16_t EP0R;                 /*!< USB Endpoint 0 register,                   Address offset: 0x00 */   __IO uint16_t RESERVED0;            /*!< Reserved */       __IO uint16_t EP1R;                 /*!< USB Endpoint 1 register,                   Address offset: 0x04 */  __IO uint16_t RESERVED1;            /*!< Reserved */         __IO uint16_t EP2R;                 /*!< USB Endpoint 2 register,                   Address offset: 0x08 */  __IO uint16_t RESERVED2;            /*!< Reserved */         __IO uint16_t EP3R;                 /*!< USB Endpoint 3 register,                   Address offset: 0x0C */   __IO uint16_t RESERVED3;            /*!< Reserved */         __IO uint16_t EP4R;                 /*!< USB Endpoint 4 register,                   Address offset: 0x10 */  __IO uint16_t RESERVED4;            /*!< Reserved */         __IO uint16_t EP5R;                 /*!< USB Endpoint 5 register,                   Address offset: 0x14 */  __IO uint16_t RESERVED5;            /*!< Reserved */         __IO uint16_t EP6R;                 /*!< USB Endpoint 6 register,                   Address offset: 0x18 */  __IO uint16_t RESERVED6;            /*!< Reserved */         __IO uint16_t EP7R;                 /*!< USB Endpoint 7 register,                   Address offset: 0x1C */  __IO uint16_t RESERVED7[17];        /*!< Reserved */       __IO uint16_t CNTR;                 /*!< Control register,                          Address offset: 0x40 */  __IO uint16_t RESERVED8;            /*!< Reserved */         __IO uint16_t ISTR;                 /*!< Interrupt status register,                 Address offset: 0x44 */  __IO uint16_t RESERVED9;            /*!< Reserved */         __IO uint16_t FNR;                  /*!< Frame number register,                     Address offset: 0x48 */  __IO uint16_t RESERVEDA;            /*!< Reserved */         __IO uint16_t DADDR;                /*!< Device address register,                   Address offset: 0x4C */  __IO uint16_t RESERVEDB;            /*!< Reserved */         __IO uint16_t BTABLE;               /*!< Buffer Table address register,             Address offset: 0x50 */  __IO uint16_t RESERVEDC;            /*!< Reserved */       } USB_TypeDef;#if defined (USB)/**   * @brief  USB Initialization Structure definition    */typedef struct{  uint32_t dev_endpoints;        /*!< Device Endpoints number.                                      This parameter depends on the used USB core.                                         This parameter must be a number between Min_Data = 1 and Max_Data = 15 */    uint32_t speed;                /*!< USB Core speed.                                      This parameter can be any value of @ref USB_Core_Speed                 */    uint32_t ep0_mps;              /*!< Set the Endpoint 0 Max Packet size.                                       This parameter can be any value of @ref USB_EP0_MPS                    */    uint32_t phy_itface;           /*!< Select the used PHY interface.                                      This parameter can be any value of @ref USB_Core_PHY                   */    uint32_t Sof_enable;           /*!< Enable or disable the output of the SOF signal.                        */    uint32_t low_power_enable;       /*!< Enable or disable Low Power mode                                      */    uint32_t lpm_enable;             /*!< Enable or disable Battery charging.                                  */    uint32_t battery_charging_enable; /*!< Enable or disable Battery charging.                                  */} USB_CfgTypeDef;typedef struct{  uint8_t   num;            /*!< Endpoint number                                This parameter must be a number between Min_Data = 1 and Max_Data = 15    */    uint8_t   is_in;          /*!< Endpoint direction                                This parameter must be a number between Min_Data = 0 and Max_Data = 1     */    uint8_t   is_stall;       /*!< Endpoint stall condition                                This parameter must be a number between Min_Data = 0 and Max_Data = 1     */    uint8_t   type;           /*!< Endpoint type                                 This parameter can be any value of @ref USB_EP_Type                      */    uint16_t  pmaadress;      /*!< PMA Address                                 This parameter can be any value between Min_addr = 0 and Max_addr = 1K   */    uint16_t  pmaaddr0;       /*!< PMA Address0                                 This parameter can be any value between Min_addr = 0 and Max_addr = 1K   */    uint16_t  pmaaddr1;        /*!< PMA Address1                                 This parameter can be any value between Min_addr = 0 and Max_addr = 1K   */    uint8_t   doublebuffer;    /*!< Double buffer enable                                 This parameter can be 0 or 1                                             */    uint16_t  tx_fifo_num;    /*!< This parameter is not required by USB Device FS peripheral, it is used                                  only by USB OTG FS peripheral                                     This parameter is added to ensure compatibility across USB peripherals   */    uint32_t  maxpacket;      /*!< Endpoint Max packet size                                 This parameter must be a number between Min_Data = 0 and Max_Data = 64KB */    uint8_t   *xfer_buff;     /*!< Pointer to transfer buffer                                               */    uint32_t  xfer_len;       /*!< Current transfer length                                                  */    uint32_t  xfer_count;     /*!< Partial transfer length in case of multi packet transfer                 */} USB_EPTypeDef;#endif /* USB */

其中USB_TypeDef结构跟STM32寄存器相关，可通过查看STM32F103C8T6参考手册来熟悉USB相关寄存器。剩余的两个结构USB_CfgTypeDef和USB_EPTypeDef跟STM32中USB模块的特性相关，因此需要多多熟悉相对应的参考手册，STM32F103C8T6可提供16个单向端点，至于PCD_HandleTypeDef中Setup数组大小为12，还不清楚为什么是12，USB协议中Setup包大小是8个字节，而这里是48个字节，后面有眉目了再说吧。对于USB器件库的使用来说PCD_HandleTypeDef结构体没有USBD_HandleTypeDef结构体重要，USBD_HandleTypeDef结构体是USB器件库中核心结构体，如下：

/* USB Device handle structure */typedef struct _USBD_HandleTypeDef{  uint8_t                 id;  uint32_t                dev_config;  uint32_t                dev_default_config;  uint32_t                dev_config_status;   USBD_SpeedTypeDef       dev_speed;   USBD_EndpointTypeDef    ep_in[15];  USBD_EndpointTypeDef    ep_out[15];    uint32_t                ep0_state;    uint32_t                ep0_data_len;       uint8_t                 dev_state;  uint8_t                 dev_old_state;  uint8_t                 dev_address;  uint8_t                 dev_connection_status;    uint8_t                 dev_test_mode;  uint32_t                dev_remote_wakeup;  USBD_SetupReqTypedef    request;  USBD_DescriptorsTypeDef *pDesc;  USBD_ClassTypeDef       *pClass;  void                    *pClassData;    void                    *pUserData;      void                    *pData;    } USBD_HandleTypeDef;/* Following USB Device Speed */typedef enum {  USBD_SPEED_HIGH  = 0,  USBD_SPEED_FULL  = 1,  USBD_SPEED_LOW   = 2,  }USBD_SpeedTypeDef;/* USB Device handle structure */typedef struct{   uint32_t                status;  uint32_t                total_length;      uint32_t                rem_length;   uint32_t                maxpacket;   } USBD_EndpointTypeDef;/** @defgroup USBD_DEF_Exported_TypesDefinitions  * @{  */typedef  struct  usb_setup_req {        uint8_t   bmRequest;                          uint8_t   bRequest;                               uint16_t  wValue;                                 uint16_t  wIndex;                                 uint16_t  wLength;                            }USBD_SetupReqTypedef;typedef struct _Device_cb{  uint8_t  (*Init)             (struct _USBD_HandleTypeDef *pdev , uint8_t cfgidx);  uint8_t  (*DeInit)           (struct _USBD_HandleTypeDef *pdev , uint8_t cfgidx); /* Control Endpoints*/  uint8_t  (*Setup)            (struct _USBD_HandleTypeDef *pdev , USBD_SetupReqTypedef  *req);    uint8_t  (*EP0_TxSent)       (struct _USBD_HandleTypeDef *pdev );      uint8_t  (*EP0_RxReady)      (struct _USBD_HandleTypeDef *pdev );    /* Class Specific Endpoints*/  uint8_t  (*DataIn)           (struct _USBD_HandleTypeDef *pdev , uint8_t epnum);     uint8_t  (*DataOut)          (struct _USBD_HandleTypeDef *pdev , uint8_t epnum);   uint8_t  (*SOF)              (struct _USBD_HandleTypeDef *pdev);   uint8_t  (*IsoINIncomplete)  (struct _USBD_HandleTypeDef *pdev , uint8_t epnum);   uint8_t  (*IsoOUTIncomplete) (struct _USBD_HandleTypeDef *pdev , uint8_t epnum);     uint8_t  *(*GetHSConfigDescriptor)(uint16_t *length);   uint8_t  *(*GetFSConfigDescriptor)(uint16_t *length);     uint8_t  *(*GetOtherSpeedConfigDescriptor)(uint16_t *length);  uint8_t  *(*GetDeviceQualifierDescriptor)(uint16_t *length);#if (USBD_SUPPORT_USER_STRING == 1)  uint8_t  *(*GetUsrStrDescriptor)(struct _USBD_HandleTypeDef *pdev ,uint8_t index,  uint16_t *length);   #endif    } USBD_ClassTypeDef;

一个USB总线最多可支持1128个设备，地址范围为0~127，因此这里用一个字节的dev_address来存储唯一的设备地址。而USBD_SetupReqTypedef结构体跟USB协议相关，USB协议中定义的Setup请求格式如下：

可以看到二者相匹配，获取setup请求更多详情，请参考USB2.0协议规范中第九章节。同时可以看到在USBD_HandleTypeDef结构体中包含了之前提到的描述符结构体USBD_DescriptorTypeDef，此外还包含了一个新的结构体设备类结构体USBD_ClassTypeDef，它里面是各个回调函数，在USB中断的回调函数中会调用设备类中的回调函数来实现具体功能，USB器件库手册中说明了设备类回调函数的作用，如下：

这些接口的实现是在CDC接口文件中实现，后面再分析，PCD_HandleTypeDef和USBD_HandleTypeDef结构通过void指针相互引用。

USB模块中静态空间分配方案实现如下：

/**  * @brief  static single allocation.  * @param  size: size of allocated memory  * @retval None  */void *USBD_static_malloc(uint32_t size){  static uint32_t mem[MAX_STATIC_ALLOC_SIZE];  return mem;}/**  * @brief  Dummy memory free  * @param  *p pointer to allocated  memory address  * @retval None  */void USBD_static_free(void *p){}

实现很简单申请一块静态空间并返回给调用者。USB设备驱动的底层API实现如下：

/*******************************************************************************                       LL Driver Interface (USB Device Library --> PCD)*******************************************************************************//**  * @brief  Initializes the Low Level portion of the Device driver.  * @param  pdev: Device handle  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_Init(USBD_HandleTypeDef *pdev){  /* Set LL Driver parameters */  hpcd.Instance = USB;  hpcd.Init.dev_endpoints = 8;//STM32F103C8T6Ö§³Ö8¸öË«Ïò¶Ëµã  hpcd.Init.ep0_mps = PCD_EP0MPS_64;//¶Ëµã0Ö§³ÖµÄ×î´ó·Ö×é×Ö½ÚÎª64  hpcd.Init.phy_itface = PCD_PHY_EMBEDDED;  hpcd.Init.speed = PCD_SPEED_FULL;//USB2.0È«ËÙÉè±¸  hpcd.Init.low_power_enable = 0;//²»Ê¹ÄÜµÍ¹¦ºÄÄ£Ê½    /* Link The driver to the stack */  hpcd.pData = pdev;  pdev->pData = &hpcd;    /* Initialize LL Driver */  HAL_PCD_Init((PCD_HandleTypeDef*)pdev->pData);  HAL_PCDEx_PMAConfig(pdev->pData , 0x00 , PCD_SNG_BUF, 0x40);//OUT¶Ëµã  HAL_PCDEx_PMAConfig(pdev->pData , 0x80 , PCD_SNG_BUF, 0x80);//IN¶Ëµã  HAL_PCDEx_PMAConfig(pdev->pData , CDC_IN_EP , PCD_SNG_BUF, 0xC0);    HAL_PCDEx_PMAConfig(pdev->pData , CDC_OUT_EP , PCD_SNG_BUF, 0x110);  HAL_PCDEx_PMAConfig(pdev->pData , CDC_CMD_EP , PCD_SNG_BUF, 0x100);   return USBD_OK;}/**  * @brief  De-Initializes the Low Level portion of the Device driver.  * @param  pdev: Device handle  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_DeInit(USBD_HandleTypeDef *pdev){  HAL_PCD_DeInit((PCD_HandleTypeDef*)pdev->pData);  return USBD_OK;}/**  * @brief  Starts the Low Level portion of the Device driver.  * @param  pdev: Device handle  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_Start(USBD_HandleTypeDef *pdev){  HAL_PCD_Start((PCD_HandleTypeDef*)pdev->pData);  return USBD_OK;}/**  * @brief  Stops the Low Level portion of the Device driver.  * @param  pdev: Device handle  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_Stop(USBD_HandleTypeDef *pdev){  HAL_PCD_Stop((PCD_HandleTypeDef*)pdev->pData);  return USBD_OK;}/**  * @brief  Opens an endpoint of the Low Level Driver.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @param  ep_type: Endpoint Type  * @param  ep_mps: Endpoint Max Packet Size  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_OpenEP(USBD_HandleTypeDef *pdev,                                  uint8_t ep_addr,                                  uint8_t ep_type,                                  uint16_t ep_mps){  HAL_PCD_EP_Open((PCD_HandleTypeDef*)pdev->pData,                  ep_addr,                  ep_mps,                  ep_type);  return USBD_OK;}/**  * @brief  Closes an endpoint of the Low Level Driver.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_CloseEP(USBD_HandleTypeDef *pdev, uint8_t ep_addr){  HAL_PCD_EP_Close((PCD_HandleTypeDef*)pdev->pData, ep_addr);  return USBD_OK;}/**  * @brief  Flushes an endpoint of the Low Level Driver.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_FlushEP(USBD_HandleTypeDef *pdev, uint8_t ep_addr){  HAL_PCD_EP_Flush((PCD_HandleTypeDef*)pdev->pData, ep_addr);  return USBD_OK;}/**  * @brief  Sets a Stall condition on an endpoint of the Low Level Driver.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_StallEP(USBD_HandleTypeDef *pdev, uint8_t ep_addr){  HAL_PCD_EP_SetStall((PCD_HandleTypeDef*)pdev->pData, ep_addr);  return USBD_OK;}/**  * @brief  Clears a Stall condition on an endpoint of the Low Level Driver.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_ClearStallEP(USBD_HandleTypeDef *pdev, uint8_t ep_addr){  HAL_PCD_EP_ClrStall((PCD_HandleTypeDef*)pdev->pData, ep_addr);  return USBD_OK;}/**  * @brief  Returns Stall condition.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @retval Stall (1: Yes, 0: No)  */uint8_t USBD_LL_IsStallEP(USBD_HandleTypeDef *pdev, uint8_t ep_addr){  PCD_HandleTypeDef *hpcd = (PCD_HandleTypeDef*)pdev->pData;  if ((ep_addr & 0x80) == 0x80)  {    return hpcd->IN_ep[ep_addr & 0x7F].is_stall;  }  else  {    return hpcd->OUT_ep[ep_addr & 0x7F].is_stall;  }}/**  * @brief  Assigns a USB address to the device.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_SetUSBAddress(USBD_HandleTypeDef *pdev, uint8_t dev_addr){  HAL_PCD_SetAddress((PCD_HandleTypeDef*)pdev->pData, dev_addr);  return USBD_OK;}/**  * @brief  Transmits data over an endpoint.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @param  pbuf: Pointer to data to be sent  * @param  size: Data size  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_Transmit(USBD_HandleTypeDef *pdev,                                    uint8_t ep_addr,                                    uint8_t *pbuf,                                    uint16_t size){  HAL_PCD_EP_Transmit((PCD_HandleTypeDef*)pdev->pData, ep_addr, pbuf, size);  return USBD_OK;}/**  * @brief  Prepares an endpoint for reception.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @param  pbuf: Pointer to data to be received  * @param  size: Data size  * @retval USBD Status  */USBD_StatusTypeDef USBD_LL_PrepareReceive(USBD_HandleTypeDef *pdev,                                          uint8_t ep_addr,                                          uint8_t *pbuf,                                          uint16_t size){  HAL_PCD_EP_Receive((PCD_HandleTypeDef*)pdev->pData, ep_addr, pbuf, size);  return USBD_OK;}/**  * @brief  Returns the last transferred packet size.  * @param  pdev: Device handle  * @param  ep_addr: Endpoint Number  * @retval Recived Data Size  */uint32_t USBD_LL_GetRxDataSize(USBD_HandleTypeDef *pdev, uint8_t ep_addr){  return HAL_PCD_EP_GetRxCount((PCD_HandleTypeDef*)pdev->pData, ep_addr);}/**  * @brief  Delays routine for the USB Device Library.  * @param  Delay: Delay in ms  * @retval None  */void USBD_LL_Delay(uint32_t Delay){  HAL_Delay(Delay);}

这些底层驱动的实现大部分都是调用Cube库中USB接口，其具体实现不必刻意关注，如果有空闲可以静心研究其寄存器的操作，我们一般只关心底层接口即可，比较复杂的一个接口是USBD_LL_Init()，USB中端点分为IN端点和OUT端点，共16个端点，在USB器件库中使用一个字节来表示，最高位为0是OUT端点，最高位为1是IN端点，USBD_LL_Init()中设置端点数为8，端点0最大包大小为64字节，为全速设备，不支持低功耗模式，并通过void指针pData来实现USBD_HandleTypeDef和PCD_HandleTypeDef结构的相互引用，HAL_PCDEx_PMAConfig()函数来设置端点缓冲区大小，这里使用了5个单向端点，有关分组缓冲的的描述可以在对应的参考手册上查找到，示例如下：

STM32中有单独的512个字节是作为USB分组缓冲区，该区域的地址为0x4000_6000~0x4000_63FF，USB和CAN模块共用该区域，因此二者不能同时访问，可以互斥访问，有关分组缓冲区有两类寄存器：USB分组缓冲区描述表地址寄存器(USB_BTABLE

);缓冲区描述表寄存器。如上图所示缓冲区描述表寄存器是几组寄存器的集合(一共8个端点共8组集合，每组里包含了4个寄存器：ADDRn_TX、COUNTn_TX、ADDRn_RX、COUNTn_RX)。这些寄存器的地址是可变的，在0x4000_6000~0x4000_63FF中，具体地址由USB_BTABLE寄存器指定，在本例中USB_BTABLE指定为0，如下：

#define BTABLE_ADDRESS                         (0x000)/*Set Btable Address*/USBx->BTABLE = BTABLE_ADDRESS;

对于每个端点的缓冲区地址及大小则由缓冲区描述表中的对应的4个寄存器来指定。分组缓冲区的访问是32bit的，所以虽然0x4000_0000~0x4000_63FF(共1K字节)，但实际上只用了512字节。此外，这也是为何USB有两种地址表示方式，一个是USB本地地址，另一个是应用程序访问USB分组缓冲地址。在示例中设置默认的控制端点的分组大小为64字节，这也和端点0的最大包大小为64相符，且都是使用的单缓冲端点，至此，usbd_conf文件分析完毕。

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