STM32 USB learning notes 2

Host environment: Windows 7 SP1

Development environment: MDK5.14

Target board: STM32F103C8T6

Development library: STM32F1Cube library and STM32_USB_Device_Library

The STM32Cube library provides some USB-related routines. In the Applications directory under its project directory, open the STM3210E_EVAL directory and you can see the following routines:

Here we select a simple example CDC_Standalone, which is a USB communication routine. The specific implementation is a USB to serial port function, which is equivalent to a USB serial port line. Copy the files in the inc and src directories in the example to the new project. Here, the files related to USB communication are placed in the vcp directory. The file directory structure is as follows:

The BSP directory is very simple. Since the purchased board only uses USB, UART modules and an LED light, the schematic diagram is as follows:

The PA15 pin is connected to an LED light as follows:

Therefore, only the operation of LED is added in the stm32f103_demo file. The source file is as follows:

/**
  ******************************************************************************
  * @file    stm32f103_demo.c
  * @author  MCD Application Team
  * @version V6.0.0
  * @date    13-October-2015
  * @brief   This file provides a set of firmware functions to manage Leds, 
  *          for STM32F103_DEMO
  ******************************************************************************
  * @attention
  *
  * 
© COPYRIGHT(c) 2014 STMicroelectronics
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  */
  
/* Includes ------------------------------------------------------------------*/
#include "STM32f103_demo.h"
 
/** @addtogroup BSP
  * @{
  */ 
 
/** @defgroup STM32F103_DEMO STM32F103-DEMO
  * @{
  */ 
 
/** @defgroup STM32F103_DEMO_Common STM32F103-DEMO Common
  * @{
  */ 
 
/** @defgroup STM32F103_DEMO_Private_TypesDefinitions Private Types Definitions
  * @{
  */ 
 
/**
  * @}
  */ 
 
/** @defgroup STM32F103_DEMO_Private_Defines Private Defines
  * @{
  */ 
 
/**
 * @brief STM32103 EVAL BSP Driver version number V6.0.0
   */
#define __STM32F103_DEMO_BSP_VERSION_MAIN       (0x06) /*!< [31:24] main version */
#define __STM32F103_DEMO_BSP_VERSION_SUB1       (0x00) /*!< [23:16] sub1 version */
#define __STM32F103_DEMO_BSP_VERSION_SUB2       (0x00) /*!< [15:8]  sub2 version */
#define __STM32F103_DEMO_BSP_VERSION_RC         (0x00) /*!< [7:0]  release candidate */
#define __STM32F103_DEMO_BSP_VERSION            ((__STM32F103_DEMO_BSP_VERSION_MAIN << 24)\
                                               |(__STM32F103_DEMO_BSP_VERSION_SUB1 << 16)\
                                               |(__STM32F103_DEMO_BSP_VERSION_SUB2 << 8 )\
                                               |(__STM32F103_DEMO_BSP_VERSION_RC))
 
/**
  * @}
  */
 
 
/** @defgroup STM32F103_DEMO_Private_Variables Private Variables
  * @{
  */ 
/**
 * @brief LED variables
 */
GPIO_TypeDef* LED_PORT[LEDn] = {LED_GPIO_PORT};
 
const uint16_t LED_PINS[LEDn] = {LED_PIN};
 
/**
  * @brief  This method returns the STM32103 EVAL BSP Driver revision
  * @retval version : 0xXYZR (8bits for each decimal, R for RC)
  */
uint32_t BSP_GetVersion(void)
{
  	return __STM32F103_DEMO_BSP_VERSION;
}
 
/**
  * @brief  Configures LED GPIO.
  * @param  Led: Specifies the Led to be configured. 
  *   This parameter can be one of following parameters:
  * @arg LED
  * @retval None
  */
void BSP_LED_Init(Led_TypeDef Led)
{
	GPIO_InitTypeDef  gpioinitstruct = {0};
 
	/* Enable the GPIO_LED clock */
	LED_GPIO_CLK_ENABLE();
	__HAL_RCC_AFIO_CLK_ENABLE();
	__HAL_AFIO_REMAP_SWJ_DISABLE();
 
	/* Configure the GPIO_LED pin */
	gpioinitstruct.Pin    = LED_PINS[Led];
	gpioinitstruct.Mode   = GPIO_MODE_OUTPUT_PP;
	gpioinitstruct.Pull   = GPIO_NOPULL;
	gpioinitstruct.Speed  = GPIO_SPEED_HIGH;
 
	HAL_GPIO_Init(LED_PORT[Led], &gpioinitstruct);
 
	HAL_GPIO_WritePin(LED_PORT[Led], LED_PINS[Led], GPIO_PIN_RESET);
}
 
/**
  * @brief  Turns selected LED On.
  * @param  Led: Specifies the Led to be set on. 
  *   This parameter can be one of following parameters:
  * @arg LED
  * @retval None
  */
void BSP_LED_On(Led_TypeDef Led)
{
  	HAL_GPIO_WritePin(LED_PORT[Led], LED_PINS[Led], GPIO_PIN_RESET);
}
 
/**
  * @brief  Turns selected LED Off.
  * @param  Led: Specifies the Led to be set off. 
  *   This parameter can be one of following parameters:
  * @arg LED
  * @retval None
  */
void BSP_LED_Off(Led_TypeDef Led)
{
  	HAL_GPIO_WritePin(LED_PORT[Led], LED_PINS[Led], GPIO_PIN_SET);
}
 
/**
  * @brief  Toggles the selected LED.
  * @param  Led: Specifies the Led to be toggled. 
  *   This parameter can be one of following parameters:
  * @arg LED
  * @retval None
  */
void BSP_LED_Toggle(Led_TypeDef Led)
{
  	HAL_GPIO_TogglePin(LED_PORT[Led], LED_PINS[Led]);
}
 
/**
  * @}
  */    
  
/**
  * @}
  */    
  
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/
 

The header file is as follows:

/**
  ******************************************************************************
  * @file    stm32f103_demo.h
  * @author  MCD Application Team
  * @version V6.0.0
  * @date    13-October-2015
  * @brief   This file contains definitions for STM32F103_DEMO's LEDs, 
  *          hardware resources.
  ******************************************************************************
  * @attention
  *
  * 
© COPYRIGHT(c) 2014 STMicroelectronics
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  */
 
/* Define to prevent recursive inclusion -------------------------------------*/
#ifndef __STM32F103_DEMO_H
#define __STM32F103_DEMO_H
 
#ifdef __cplusplus
 extern "C" {
#endif 
 
/** @addtogroup BSP
  * @{
  */ 
 
/** @addtogroup STM32F103_DEMO
  * @{
  */ 
 
/* Includes ------------------------------------------------------------------*/
#include "stm32f1xx_hal.h"
 
/** @addtogroup STM32F103_DEMO_Common STM3210E-EVAL Common
  * @{
  */ 
 
/** @defgroup STM32F103_DEMO_Exported_Types Exported Types
  * @{
  */
 
/**
 * @brief LED Types Definition
 */
typedef enum 
{
  LED = 0,
 
  LED_GREEN  = LED,
 
} Led_TypeDef;
 
/**
  * @}
  */ 
 
/** @defgroup STM32F103_DEMO_Exported_Constants Exported Constants
  * @{
  */ 
 
/** 
  * @brief  Define for STM32F103_DEMO board  
  */ 
#if !defined (USE_STM32F103_DEMO)
 #define USE_STM32F103_DEMO
#endif
  
/** @addtogroup STM32F103_DEMO_LED
  * @{
  */
#define LEDn                             1
 
#define LED_PIN                         GPIO_PIN_15             /* PA.15*/
#define LED_GPIO_PORT                   GPIOA
#define LED_GPIO_CLK_ENABLE()           __HAL_RCC_GPIOA_CLK_ENABLE()
#define LED_GPIO_CLK_DISABLE()          __HAL_RCC_GPIOA_CLK_DISABLE()
 
/** @addtogroup STM32F103_DEMO_Exported_Functions
  * @{
  */ 
uint32_t                BSP_GetVersion(void);
void                    BSP_LED_Init(Led_TypeDef Led);
void                    BSP_LED_On(Led_TypeDef Led);
void                    BSP_LED_Off(Led_TypeDef Led);
void                    BSP_LED_Toggle(Led_TypeDef Led);
 
/**
  * @}
  */
  
/**
  * @}
  */
  
#ifdef __cplusplus
}
#endif
  
#endif /* __STM32F103_DEMO_H */
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

There is almost no change in other files, just change the content of the referenced stm32f10e_eval.h header file to stm32f13_demo.h. It should be noted that the PA15 port is used as a debug interface when the STM32 is running normally, so the debug function needs to be disabled, which is reflected in the BSP_LED_Init() function. Compile the code and download it to the target board.
Before running the code, we need to install a USB serial port driver: VCP_1.40_Setup, which can be found on the ST official website. With it, our USB can be identified as a serial port on the host and can be operated using the serial port. After the hardware is connected, we can see that there are two serial ports through the device manager, as follows:

COM5 is the actual serial port of the board, and COM6 is a virtual serial port created by USB. By opening two serial terminals, serial communication can be achieved as follows:

The information sent from COM5 can be received in COM6, and the information sent from COM6 can be received in COM5. At the same time, the DEMO supports the modification of the serial port baud rate. We change the baud rate of COM6 and COM5 to 57600 and continue to communicate. It is still possible, as follows:


Of course, except for the baud rate, the data bit, stop bit, and check bit can all be modified normally. With these intuitive functional descriptions, it will be easier for us to understand the use of the USB CDC class. Next, let's analyze the code implementation of VCP step by step.
First, let's analyze the processing of physical hardware, that is, the stm32f1xx_hal_msp,c file. This file is very simple and just initializes the IO resources of UART.


/**
  ******************************************************************************
  * @file    USB_Device/CDC_Standalone/Src/stm32f1xx_hal_msp.c
  * @author  MCD Application Team
  * @version V1.2.0
  * @date    31-July-2015
  * @brief   HAL MSP module.
  ******************************************************************************
  * @attention
  *
  * 
© COPYRIGHT(c) 2015 STMicroelectronics
  *
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  *   1. Redistributions of source code must retain the above copyright notice,
  *      this list of conditions and the following disclaimer.
  *   2. Redistributions in binary form must reproduce the above copyright notice,
  *      this list of conditions and the following disclaimer in the documentation
  *      and/or other materials provided with the distribution.
  *   3. Neither the name of STMicroelectronics nor the names of its contributors
  *      may be used to endorse or promote products derived from this software
  *      without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  ******************************************************************************
  */
 
/* Includes ------------------------------------------------------------------*/
#include "main.h"
 
/** @addtogroup USBD_USER
* @{
*/
 
/** @defgroup USBD_USR_MAIN
  * @brief This file is the CDC application main file
  * @{
  */
 
/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
/* Private function prototypes -----------------------------------------------*/
/* Private functions ---------------------------------------------------------*/
 
/**
  * @brief UART MSP Initialization
  *        This function configures the hardware resources used in this example:
  *           - Peripheral's clock enable
  *           - Peripheral's GPIO Configuration
  *           - DMA configuration for transmission request by peripheral
  *           - NVIC configuration for DMA interrupt request enable
  * @param huart: UART handle pointer
  * @retval None
  */
void HAL_UART_MspInit(UART_HandleTypeDef *huart)
{
  static DMA_HandleTypeDef hdma_tx;
  GPIO_InitTypeDef  GPIO_InitStruct;
 
  /*##-1- Enable peripherals and GPIO Clocks #################################*/
  /* Enable GPIO clock */
  USARTx_TX_GPIO_CLK_ENABLE();
  USARTx_RX_GPIO_CLK_ENABLE();
 
  /* Enable USARTx clock */
  USARTx_CLK_ENABLE();
 
  /* Enable DMA clock */
  DMAx_CLK_ENABLE();
 
  /*##-2- Configure peripheral GPIO ##########################################*/
  /* UART TX GPIO pin configuration  */
  GPIO_InitStruct.Pin = USARTx_TX_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
  GPIO_InitStruct.Pull      = GPIO_PULLUP;
  GPIO_InitStruct.Speed     = GPIO_SPEED_HIGH;
 
  HAL_GPIO_Init(USARTx_TX_GPIO_PORT, &GPIO_InitStruct);
 
  /* UART RX GPIO pin configuration  */
  GPIO_InitStruct.Pin = USARTx_RX_PIN;
  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
  HAL_GPIO_Init(USARTx_RX_GPIO_PORT, &GPIO_InitStruct);
  
  /*##-3- Configure the NVIC for UART ########################################*/   
  HAL_NVIC_SetPriority(USARTx_IRQn, 4, 0);
  HAL_NVIC_EnableIRQ(USARTx_IRQn);
 
  /*##-4- Configure the DMA channels ##########################################*/
  /* Configure the DMA handler for Transmission process */
  hdma_tx.Instance                 = USARTx_TX_DMA_STREAM;
  hdma_tx.Init.Direction           = DMA_MEMORY_TO_PERIPH;
  hdma_tx.Init.PeriphInc           = DMA_PINC_DISABLE;
  hdma_tx.Init.MemInc              = DMA_MINC_ENABLE;
  hdma_tx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
  hdma_tx.Init.MemDataAlignment    = DMA_MDATAALIGN_BYTE;
  hdma_tx.Init.Mode                = DMA_NORMAL;
  hdma_tx.Init.Priority            = DMA_PRIORITY_LOW;
 
  HAL_DMA_Init(&hdma_tx);
  
  /* Associate the initialized DMA handle to the UART handle */
  __HAL_LINKDMA(huart, hdmatx, hdma_tx);
  
  /*##-5- Configure the NVIC for DMA #########################################*/
  /* NVIC configuration for DMA transfer complete interrupt (USARTx_TX) */
  HAL_NVIC_SetPriority(USARTx_DMA_TX_IRQn, 5, 0);
  HAL_NVIC_EnableIRQ(USARTx_DMA_TX_IRQn);
  
  /*##-6- Enable TIM peripherals Clock #######################################*/
  TIMx_CLK_ENABLE();
  
  /*##-7- Configure the NVIC for TIMx ########################################*/
  /* Set Interrupt Group Priority */ 
  HAL_NVIC_SetPriority(TIMx_IRQn, 5, 0);
  
  /* Enable the TIMx global Interrupt */
  HAL_NVIC_EnableIRQ(TIMx_IRQn);
}
 
/**
  * @brief UART MSP De-Initialization
  *        This function frees the hardware resources used in this example:
  *          - Disable the Peripheral's clock
  *          - Revert GPIO, DMA and NVIC configuration to their default state
  * @param huart: UART handle pointer
  * @retval None
  */
void HAL_UART_MspDeInit(UART_HandleTypeDef *huart)
{
  /*##-1- Reset peripherals ##################################################*/
  USARTx_FORCE_RESET();
  USARTx_RELEASE_RESET();
 
  /*##-2- Disable peripherals and GPIO Clocks #################################*/
  /* Configure UART Tx as alternate function  */
  HAL_GPIO_DeInit(USARTx_TX_GPIO_PORT, USARTx_TX_PIN);
  /* Configure UART Rx as alternate function  */
  HAL_GPIO_DeInit(USARTx_RX_GPIO_PORT, USARTx_RX_PIN);
 
  /*##-3- Disable the NVIC for UART ##########################################*/
  HAL_NVIC_DisableIRQ(USARTx_IRQn);
  
  /*##-4- Disable the NVIC for DMA ###########################################*/
  HAL_NVIC_DisableIRQ(USARTx_DMA_TX_IRQn);
  
  /*##-5- Reset TIM peripheral ###############################################*/
  TIMx_FORCE_RESET();
  TIMx_RELEASE_RESET();
}
 
/**
  * @}
  */
 
/**
  * @}
  */
 
/**
  * @}
  */
 
/************************ (C) COPYRIGHT STMicroelectronics *****END OF FILE****/

Three interrupts are enabled here: UART1 interrupt, DMA1 channel 4 (UART_TX) interrupt, TIM3 timer interrupt. The initialization of these IO resources is relatively simple, clear and easy to understand. The reason why UARTIO resources are initialized here is because this DEMO implements the function of USB to serial port, that is, the data received from the UART port is sent out from the USB port, and the data received from the USB port is sent out from the UART port. The initialization of the IO resources of the USB port is in another file. The role of the timer is reflected in another file, although it is not clear why the timer is enabled here instead of being put together with its initialization. . .
Normally, USB devices add pull-up resistors to D+ and D- to detect device connection and disconnection events. In the example, an IO is used to dynamically pull up and down. The board I bought here does not have an IO port connected and directly uses a 1.5K pull-up resistor, so there is no need for a separate IO port control, as shown in the figure:

Just remove the pull-up resistor control code in the usbd_conf.c file, which involves the HAL_PCD_MspInit() function and the HAL_PCDEx_SetConnectionState() function. Modify them as follows:


/**
  * @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  Software Device Connection
  * @param  hpcd: PCD handle
  * @param  state: connection state (0 : disconnected / 1: connected)
  * @retval None
  */
void HAL_PCDEx_SetConnectionState(PCD_HandleTypeDef *hpcd, uint8_t state)
{
 
}

Finally, slightly modify the Toggle_Leds() function in the main function to change the cumulative counter to be cleared after increasing to 1000, that is, flipping every 1S, as follows:

/**
  * @brief  Toggle LEDs to shows user input state.
  * @param  None
  * @retval None
  */
void Toggle_Leds(void)
{
	static uint32_t ticks;
 
	if (ticks++ == 1000)
	{
		BSP_LED_Toggle(LED);
		ticks = 0;
	}
}

At this point, the basic code has been modified, and all that remains is to analyze the code.