stm32 usb通信

STM32芯片内置USB控制器，可以通过USB接口与主机或其他设备进行通信。在使用USB通信之前，需要对STM32的USB控制器进行配置和初始化。

下面是一个简单的STM32 USB通信的例程，实现了从主机接收数据并通过串口输出的功能：

#include "stm32f10x.h"
#include "usb_lib.h"
#include "usb_desc.h"
#include "usb_pwr.h"

#define USART_TX_GPIO_PORT       GPIOA   
#define USART_TX_GPIO_CLK        RCC_APB2Periph_GPIOA
#define USART_TX_PIN             GPIO_Pin_9

#define USART_RX_GPIO_PORT       GPIOA   
#define USART_RX_GPIO_CLK        RCC_APB2Periph_GPIOA
#define USART_RX_PIN             GPIO_Pin_10

void RCC_Configuration(void)
{
  /* Enable GPIO clock */
  RCC_APB2PeriphClockCmd(USART_TX_GPIO_CLK | USART_RX_GPIO_CLK, ENABLE);
}

void GPIO_Configuration(void)
{
  GPIO_InitTypeDef GPIO_InitStructure;

  /* Configure USART Tx as alternate function push-pull */
  GPIO_InitStructure.GPIO_Pin = USART_TX_PIN;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_Init(USART_TX_GPIO_PORT, &GPIO_InitStructure);

  /* Configure USART Rx as input floating */
  GPIO_InitStructure.GPIO_Pin = USART_RX_PIN;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
  GPIO_Init(USART_RX_GPIO_PORT, &GPIO_InitStructure);
}

void USART_Configuration(void)
{
  USART_InitTypeDef USART_InitStructure;

  /* USART1 configuration ------------------------------------------------------*/
  /* USART1 configured as follow:
        - BaudRate = 115200 baud  
        - Word Length = 8 Bits
        - One Stop Bit
        - No parity
        - Hardware flow control disabled (RTS and CTS signals)
        - Receive and transmit enabled
  */
  USART_InitStructure.USART_BaudRate = 115200;
  USART_InitStructure.USART_WordLength = USART_WordLength_8b;
  USART_InitStructure.USART_StopBits = USART_StopBits_1;
  USART_InitStructure.USART_Parity = USART_Parity_No;
  USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
  USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;

  /* Configure USART */
  USART_Init(USART1, &USART_InitStructure);

  /* Enable USART */
  USART_Cmd(USART1, ENABLE);
}

void USB_Configuration(void)
{
  Set_USBClock();
  USB_Interrupts_Config();
  USB_Init();
}

int main(void)
{
  RCC_Configuration();
  GPIO_Configuration();
  USART_Configuration();
  USB_Configuration();

  while (1)
  {
    if (bDeviceState == CONFIGURED)
    {
      uint8_t buffer[64];
      uint16_t length = USB_SIL_Read(EP1_OUT, buffer);

      if (length > 0)
      {
        USART_SendData(USART1, buffer[0]);
        while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);
      }
    }
  }
}

需要注意的是，这个例程中使用的是CDC（Communication Device Class）通信协议，因此需要在usb_desc.c文件中定义相应的描述符。同时，还需要实现一些回调函数，比如USB中断处理函数、USB数据发送函数等。

另外，需要在STM32CubeMX中进行一些配置，比如启用USB功能、配置PLL时钟等。具体的步骤可以参考ST官方文档或者相关的教程。