STM32 USB学习笔记5

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

承接前文，对于上层应用而言只剩下CDC类接口文件即usbd_cdc_interface，该文件主要为实现CDC类接口所用到的物理资源以及逻辑资源，需要参考通信设备通用串行总线类定义版本1.2以及PSTN设备通用串行总线通信类子类规范版本1.2，这两个文档都可以在USB组织官网上下载得到，首先看下usbd_cdc_interface.h文件，如下：

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

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

/* Exported types ------------------------------------------------------------*/
/* Exported constants --------------------------------------------------------*/
/* User can use this section to tailor USARTx/UARTx instance used and associated
resources */
/* Definition for USARTx clock resources */
#define USARTx USART1
#define USARTx_CLK_ENABLE() __HAL_RCC_USART1_CLK_ENABLE();
#define DMAx_CLK_ENABLE() __HAL_RCC_DMA1_CLK_ENABLE()
#define USARTx_RX_GPIO_CLK_ENABLE() __HAL_RCC_GPIOA_CLK_ENABLE()
#define USARTx_TX_GPIO_CLK_ENABLE() __HAL_RCC_GPIOA_CLK_ENABLE()

#define USARTx_FORCE_RESET() __HAL_RCC_USART1_FORCE_RESET()
#define USARTx_RELEASE_RESET() __HAL_RCC_USART1_RELEASE_RESET()

/* Definition for USARTx Pins */
#define USARTx_TX_PIN GPIO_PIN_9
#define USARTx_TX_GPIO_PORT GPIOA
#define USARTx_RX_PIN GPIO_PIN_10
#define USARTx_RX_GPIO_PORT GPIOA

/* Definition for USARTx's NVIC: used for receiving data over Rx pin */
#define USARTx_IRQn USART1_IRQn
#define USARTx_IRQHandler USART1_IRQHandler

/* Definition for USARTx's DMA: used for transmitting data over Tx pin */
#define USARTx_TX_DMA_STREAM DMA1_Channel4
#define USARTx_RX_DMA_STREAM DMA1_Channel5

/* Definition for USARTx's NVIC */
#define USARTx_DMA_TX_IRQn DMA1_Channel4_IRQn
#define USARTx_DMA_RX_IRQn DMA1_Channel5_IRQn
#define USARTx_DMA_TX_IRQHandler DMA1_Channel4_IRQHandler
#define USARTx_DMA_RX_IRQHandler DMA1_Channel5_IRQHandler

/* Definition for TIMx clock resources */
#define TIMx TIM3
#define TIMx_CLK_ENABLE __HAL_RCC_TIM3_CLK_ENABLE
#define TIMx_FORCE_RESET() __HAL_RCC_USART1_FORCE_RESET()
#define TIMx_RELEASE_RESET() __HAL_RCC_USART1_RELEASE_RESET()

/* Definition for TIMx's NVIC */
#define TIMx_IRQn TIM3_IRQn
#define TIMx_IRQHandler TIM3_IRQHandler

/* Periodically, the state of the buffer "UserTxBuffer" is checked.
The period depends on CDC_POLLING_INTERVAL */
#define CDC_POLLING_INTERVAL 5 /* in ms. The max is 65 and the min is 1 */

extern USBD_CDC_ItfTypeDef USBD_CDC_fops;

/* Exported macro ------------------------------------------------------------*/
/* Exported functions ------------------------------------------------------- */
#endif /* __USBD_CDC_IF_H */

/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
这其中主要是一些物理资源的定义，需要用到一个串口资源(且使用DMA方式发送数据)，一个定时器资源(定时读取从串口接收到的数据并发往USB接口)。这里虽然列出了两个DMA通道，但在实现中只用到了TX的DMA发送一个通道，文件末尾有一个CDC类接口数据结构USBD_CDC_ItfTypeDef，如下：

typedef struct _USBD_CDC_Itf
{
int8_t (* Init) (void);
int8_t (* DeInit) (void);
int8_t (* Control) (uint8_t, uint8_t * , uint16_t);
int8_t (* Receive) (uint8_t *, uint32_t *);

}USBD_CDC_ItfTypeDef;有关该结构的说明可以在USB器件库文档中找到，如下：



由上可以看出这里只有OUT传输而没有IN传输，VCP模型很简单就只有简单的收发数据以及一些属性的修改等，因此这里的CDC接口接口内容不多。下面查看一下usbd_cdc_interface.c文件，其内容是CDC类物理以及逻辑接口的具体实现。文件开头申请了两块缓冲区用于数据的收发，如下：

#define APP_RX_DATA_SIZE 2048
#define APP_TX_DATA_SIZE 2048

uint8_t UserRxBuffer[APP_RX_DATA_SIZE];/* Received Data over USB are stored in this buffer */
uint8_t UserTxBuffer[APP_TX_DATA_SIZE];/* Received Data over UART (CDC interface) are stored in this buffer */
uint32_t BuffLength;
uint32_t UserTxBufPtrIn = 0;/* Increment this pointer or roll it back to
start address when data are received over USART */
uint32_t UserTxBufPtrOut = 0; /* Increment this pointer or roll it back to
start address when data are sent over USB */

两块缓冲区是循环使用，其中的RX、TX是针对USB模块而言，各2K字节。在文件头部还有一个新的数据结构USBD_CDC_LineCodingTypeDef，该结构很简单，如下：

typedef struct
{
uint32_t bitrate;
uint8_t format;
uint8_t paritytype;
uint8_t datatype;
}USBD_CDC_LineCodingTypeDef;对应着串口的各个属性，有关LineCoding的相关信息可以在PSTN120文档中找到，如下：



并且罗列了各个属性的取值范围，由此可以看出默认状态下串口属性为：115200波特率、1个停止位，8个数据位，无校验。接着查看CDC类接口的实现函数，首先是硬件资源的初始化操作：

USBD_CDC_ItfTypeDef USBD_CDC_fops =
{
CDC_Itf_Init,
CDC_Itf_DeInit,
CDC_Itf_Control,
CDC_Itf_Receive
};

/* Private functions ---------------------------------------------------------*/

/**
* @brief CDC_Itf_Init
* Initializes the CDC media low layer
* @param None
* @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
*/
static int8_t CDC_Itf_Init(void)
{
/*##-1- Configure the UART peripheral ######################################*/
/* Put the USART peripheral in the Asynchronous mode (UART Mode) */
/* USART configured as follows:
- Word Length = 8 Bits
- Stop Bit = One Stop bit
- Parity = No parity
- BaudRate = 115200 baud
- Hardware flow control disabled (RTS and CTS signals) */
UartHandle.Instance = USARTx;
UartHandle.Init.BaudRate = 115200;
UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
UartHandle.Init.StopBits = UART_STOPBITS_1;
UartHandle.Init.Parity = UART_PARITY_NONE;
UartHandle.Init.HwFlowCtl = UART_HWCONTROL_NONE;
UartHandle.Init.Mode = UART_MODE_TX_RX;

if(HAL_UART_Init(&UartHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}

/*##-2- Put UART peripheral in IT reception process ########################*/
/* Any data received will be stored in "UserTxBuffer" buffer */
if(HAL_UART_Receive_IT(&UartHandle, (uint8_t *)UserTxBuffer, 1) != HAL_OK)
{
/* Transfer error in reception process */
Error_Handler();
}

/*##-3- Configure the TIM Base generation #################################*/
TIM_Config();

/*##-4- Start the TIM Base generation in interrupt mode ####################*/
/* Start Channel1 */
if(HAL_TIM_Base_Start_IT(&TimHandle) != HAL_OK)
{
/* Starting Error */
Error_Handler();
}

/*##-5- Set Application Buffers ############################################*/
USBD_CDC_SetTxBuffer(&USBD_Device, UserTxBuffer, 0);
USBD_CDC_SetRxBuffer(&USBD_Device, UserRxBuffer);

return (USBD_OK);
}

/**
* @brief CDC_Itf_DeInit
* DeInitializes the CDC media low layer
* @param None
* @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
*/
static int8_t CDC_Itf_DeInit(void)
{
/* DeInitialize the UART peripheral */
if(HAL_UART_DeInit(&UartHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
return (USBD_OK);
}这里主要是串口资源的初始化，按照LineCoding中默认的属性初始化串口资源，并进一步调用之前stm32f1xx_hal_msp.c文件中的HAL_UART_MspInit()，HAL_UART_MspDeInit()方法。此外开启串口接收中断接收字节数据，同时初始化定时器资源，如下：

/**
* @brief TIM_Config: Configure TIMx timer
* @param None.
* @retval None.
*/
static void TIM_Config(void)
{
/* Set TIMx instance */
TimHandle.Instance = TIMx;

/* Initialize TIM3 peripheral as follows:
+ Period = 10000 - 1
+ Prescaler = ((SystemCoreClock/2)/10000) - 1
+ ClockDivision = 0
+ Counter direction = Up
*/
TimHandle.Init.Period = (CDC_POLLING_INTERVAL*1000) - 1;
TimHandle.Init.Prescaler = 84-1;
TimHandle.Init.ClockDivision = 0;
TimHandle.Init.CounterMode = TIM_COUNTERMODE_UP;
if(HAL_TIM_Base_Init(&TimHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}
}
这个没什么说的，在CDC_Itf_Init()函数的末尾有两个设置缓冲区的函数，USBD_CDC_SetTxBuffer()、USBD_CDC_SetRxBuffer()，这两个函数在USB器件库的类文件中，后面再分析，这里知道其作用即可。下面类分析CDC_Itf_Control()函数，该函数管理CDC类请求，如下：

/**
* @brief CDC_Itf_Control
* Manage the CDC class requests
* @param Cmd: Command code
* @param Buf: Buffer containing command data (request parameters)
* @param Len: Number of data to be sent (in bytes)
* @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
*/
static int8_t CDC_Itf_Control (uint8_t cmd, uint8_t* pbuf, uint16_t length)
{
switch (cmd)
{
case CDC_SEND_ENCAPSULATED_COMMAND:
/* Add your code here */
break;

case CDC_GET_ENCAPSULATED_RESPONSE:
/* Add your code here */
break;

case CDC_SET_COMM_FEATURE:
/* Add your code here */
break;

case CDC_GET_COMM_FEATURE:
/* Add your code here */
break;

case CDC_CLEAR_COMM_FEATURE:
/* Add your code here */
break;

case CDC_SET_LINE_CODING:
LineCoding.bitrate = (uint32_t)(pbuf[0] | (pbuf[1] << 8) |\
(pbuf[2] << 16) | (pbuf[3] << 24));
LineCoding.format = pbuf[4];
LineCoding.paritytype = pbuf[5];
LineCoding.datatype = pbuf[6];

/* Set the new configuration */
ComPort_Config();
break;

case CDC_GET_LINE_CODING:
pbuf[0] = (uint8_t)(LineCoding.bitrate);
pbuf[1] = (uint8_t)(LineCoding.bitrate >> 8);
pbuf[2] = (uint8_t)(LineCoding.bitrate >> 16);
pbuf[3] = (uint8_t)(LineCoding.bitrate >> 24);
pbuf[4] = LineCoding.format;
pbuf[5] = LineCoding.paritytype;
pbuf[6] = LineCoding.datatype;

/* Add your code here */
break;

case CDC_SET_CONTROL_LINE_STATE:
/* Add your code here */
break;

case CDC_SEND_BREAK:
/* Add your code here */
break;

default:
break;
}

return (USBD_OK);
}USB请求在USB器件库文档中分为三类：标准请求、特定类请求、特定厂商请求。其中标准请求由默认的控制端点0接收处理，另外两类请求由回调函数传递到特定类代码进行处理，这里的CDC_Itf_Control()函数即为回调函数最终实现者，其处理CDC类的特定请求，这些请求可以在PSTN120协议文档以及CDC120协议文档中找到，如下：



在CDC_Itf_Control()可以处理以上请求，但在具体实现上只处理了个别请求，即SET_LINE_CODING和GET_LINE_CODING，代码中各个请求的定义如下：

/*---------------------------------------------------------------------*/
/* CDC definitions */
/*---------------------------------------------------------------------*/
#define CDC_SEND_ENCAPSULATED_COMMAND 0x00
#define CDC_GET_ENCAPSULATED_RESPONSE 0x01
#define CDC_SET_COMM_FEATURE 0x02
#define CDC_GET_COMM_FEATURE 0x03
#define CDC_CLEAR_COMM_FEATURE 0x04
#define CDC_SET_LINE_CODING 0x20
#define CDC_GET_LINE_CODING 0x21
#define CDC_SET_CONTROL_LINE_STATE 0x22
#define CDC_SEND_BREAK 0x23可以看到各个请求的值与PSTN120协议文档中的值相一致，而CDC_SEND_ENCAPSULATED_COMMAND和CDC_SEND_ENCAPSULATED_RESPONSE的值没有在PSTN120协议文档中，其是在CDC120协议文档中定义的。当我们在PC端上的串口工具中修改串口通信的属性时就会触发CDC_SET_LINE_CODING请求，同时也可以通过CDC_GET_LINE_CODING请求来获取当前串口通信的属性值，在CDC_SET_LINE_CODING请求中通过ComPort_Config()函数类重新配置串口，如下：

/**
* @brief ComPort_Config
* Configure the COM Port with the parameters received from host.
* @param None.
* @retval None.
* @note When a configuration is not supported, a default value is used.
*/
static void ComPort_Config(void)
{
if(HAL_UART_DeInit(&UartHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}

/* set the Stop bit */
switch (LineCoding.format)
{
case 0:
UartHandle.Init.StopBits = UART_STOPBITS_1;
break;
case 2:
UartHandle.Init.StopBits = UART_STOPBITS_2;
break;
default :
UartHandle.Init.StopBits = UART_STOPBITS_1;
break;
}

/* set the parity bit*/
switch (LineCoding.paritytype)
{
case 0:
UartHandle.Init.Parity = UART_PARITY_NONE;
break;
case 1:
UartHandle.Init.Parity = UART_PARITY_ODD;
break;
case 2:
UartHandle.Init.Parity = UART_PARITY_EVEN;
break;
default :
UartHandle.Init.Parity = UART_PARITY_NONE;
break;
}

/*set the data type : only 8bits and 9bits is supported */
switch (LineCoding.datatype)
{
case 0x07:
/* With this configuration a parity (Even or Odd) must be set */
UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
break;
case 0x08:
if(UartHandle.Init.Parity == UART_PARITY_NONE)
{
UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
}
else
{
UartHandle.Init.WordLength = UART_WORDLENGTH_9B;
}

break;
default :
UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
break;
}

UartHandle.Init.BaudRate = LineCoding.bitrate;
UartHandle.Init.HwFlowCtl = UART_HWCONTROL_NONE;
UartHandle.Init.Mode = UART_MODE_TX_RX;

if(HAL_UART_Init(&UartHandle) != HAL_OK)
{
/* Initialization Error */
Error_Handler();
}

/* Start reception: provide the buffer pointer with offset and the buffer size */
HAL_UART_Receive_IT(&UartHandle, (uint8_t *)(UserTxBuffer + UserTxBufPtrIn), 1);
}在ComPort_Config()函数的最后再次开启串口接收中断用于接收字节数据，在缓冲区后面追加。SetLineConding和GetLineCoding请求的数据格式如下：



这个要配合SETUP包的结构定义才方便理解，如SetLineCoding请求中bmRequestType值为00100001B对照SETUP包结构可知其为类请求且接收者是接口，wValue为0，wIndex为接口号，wLength为后面数据长度，针对Line Coding结构而言该值为7，wIndex的值在接收者为端点和接口时含义不同，如下：



对于此例而言我们使用的是后者，即低8位标记接口号。接着分析CDC_Itf_Receive()函数，如下：

/**
* @brief CDC_Itf_DataRx
* Data received over USB OUT endpoint are sent over CDC interface
* through this function.
* @param Buf: Buffer of data to be transmitted
* @param Len: Number of data received (in bytes)
* @retval Result of the opeartion: USBD_OK if all operations are OK else USBD_FAIL
*/
static int8_t CDC_Itf_Receive(uint8_t* Buf, uint32_t *Len)
{
HAL_UART_Transmit_DMA(&UartHandle, Buf, *Len);
return (USBD_OK);
}该函数也很简单，将从USB接口收到的数据直接通过串口DMA方式发送出去，至此CDC类接口的回调函数分析完毕，还剩下几个中断回调函数，首先看下串口接收中断回调函数，如下：

/**
* @brief Rx Transfer completed callback
* @param huart: UART handle
* @retval None
*/
void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
/* Increment Index for buffer writing */
UserTxBufPtrIn++;

/* To avoid buffer overflow */
if(UserTxBufPtrIn == APP_RX_DATA_SIZE)
{
UserTxBufPtrIn = 0;
}

/* Start another reception: provide the buffer pointer with offset and the buffer size */
HAL_UART_Receive_IT(huart, (uint8_t *)(UserTxBuffer + UserTxBufPtrIn), 1);
}该回调很简单循环使用USB发送缓冲区，当接收完一个字节后移动USB发送缓冲区下标立即开启下一个字节的接收。接着查看串口发送完成中断回调函数，虽然这里串口发送是使用DMA方式，但在Cube库中会开启三个中断回调函数:半传输完成、传输完成以及错误处理，其中传输完成的回调函数中会进一步调用串口发送完成的回调函数，同时，错误处理的回调函数也会进一步调用串口的错误回调函数，二者如下：

/**
* @brief Tx Transfer completed callback
* @param huart: UART handle
* @retval None
*/
void HAL_UART_TxCpltCallback(UART_HandleTypeDef *huart)
{
/* Initiate next USB packet transfer once UART completes transfer (transmitting data over Tx line) */
USBD_CDC_ReceivePacket(&USBD_Device);
}

/**
* @brief UART error callbacks
* @param UartHandle: UART handle
* @retval None
*/
void HAL_UART_ErrorCallback(UART_HandleTypeDef *UartHandle)
{
/* Transfer error occured in reception and/or transmission process */
Error_Handler();
}这里主要看下串口发送完成中断回调函数，其调用USBD_CDC_ReveivePacket()函数来开启下一个USB数据包的接收，该函数在后面再具体分析。现在就只剩下定时器回调函数了，前面已经分析如何把从USB接收到的数据通过串口发送出去，但从串口接收到的数据还没有通过USB发出，定时器的回调函数就是实现该过程的，如下：

/**
* @brief TIM period elapsed callback
* @param htim: TIM handle
* @retval None
*/
void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
uint32_t buffptr;
uint32_t buffsize;

if(UserTxBufPtrOut != UserTxBufPtrIn)
{
if(UserTxBufPtrOut > UserTxBufPtrIn) /* rollback */
{
buffsize = APP_RX_DATA_SIZE - UserTxBufPtrOut;
}
else
{
buffsize = UserTxBufPtrIn - UserTxBufPtrOut;
}

buffptr = UserTxBufPtrOut;

USBD_CDC_SetTxBuffer(&USBD_Device, (uint8_t*)&UserTxBuffer[buffptr], buffsize);

if(USBD_CDC_TransmitPacket(&USBD_Device) == USBD_OK)
{
UserTxBufPtrOut += buffsize;
if (UserTxBufPtrOut == APP_RX_DATA_SIZE)
{
UserTxBufPtrOut = 0;
}
}
}
}首先是判断UserTxBufPtrOut和UserTxBufPtrIn是否相等以便检测是否在串口中收到了数据，如果不想等则表明在串口中接收到了数据，就要将这些数据通过USB模块发送出去，二者不相等时就需要计算需要通过USB发送的字节数即buffsize的计算，Out比In大时表明缓冲区有循环，则先把末尾数据发送完毕，等下次定时器达到时再从头发送即可。计算完数据量后通过USBD_CDC_SetTxBuffer()函数来设置发送缓冲区及数据大小，通过USBD_CDC_TransmitPacket()函数来开启USB发送，并更新UserTxBufPtrOut数值。至此usbd_cdc_interface文件分析完毕，后面可以开始分析USB器件库了。