原创 USART--通用同步异步收发机

　　USART提供了一种灵活的方法来与使用工业标准NRZ异步串行数据格式的外部设备之间进行全双工数据交换。USART利用分数波特率发生器提供宽范围的波特率选择。本身USART比较复杂，但是在这里我只是用来调试，也就是把数据从设备发到主机，所以我们暂且把这一部分实现，我们把更多的时间转到USB通信，因为这是趋势。下面给出一个USART的具体的例子。

/**
  ******************************************************************************
  * @file    Project/Template/main.c
  * @author  MCD Application Team
  * @version V3.0.0
  * @date    04/06/2009
  * @brief   Main program body
  ******************************************************************************
  * @copy
  *
  * 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 2009 STMicroelectronics</center></h2>
  */

/* Includes ------------------------------------------------------------------*/
#include "stm32f10x.h"
#include "stm32f10x_conf.h"
#include<string.h>

/** @addtogroup Template_Project
  * @{
  */

/* Private typedef -----------------------------------------------------------*/
/* Private define ------------------------------------------------------------*/
/* Private macro -------------------------------------------------------------*/
/* Private variables ---------------------------------------------------------*/
char *SendData;

/* Private function prototypes -----------------------------------------------*/
/* Private functions ---------------------------------------------------------*/
void RCC_Config()
{
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA|RCC_APB2Periph_AFIO,ENABLE);
}

void GPIO_Config()
{
  GPIO_InitTypeDef GPIO_InitStructure;
  GPIO_InitStructure.GPIO_Pin=GPIO_Pin_9;
  GPIO_InitStructure.GPIO_Speed=GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode=GPIO_Mode_AF_PP;
  GPIO_Init(GPIOA,&GPIO_InitStructure);
 
  GPIO_InitStructure.GPIO_Pin=GPIO_Pin_10;
  GPIO_InitStructure.GPIO_Mode=GPIO_Mode_IN_FLOATING;
  GPIO_Init(GPIOA,&GPIO_InitStructure);
}

void NVIC_Config()
{
  NVIC_InitTypeDef NVIC_InitStructure;
 
  NVIC_PriorityGroupConfig(NVIC_PriorityGroup_0);
  NVIC_InitStructure.NVIC_IRQChannel=USART1_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=0;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority=0;
  NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;
  NVIC_Init(&NVIC_InitStructure);
}

void USART_Config()
{
  USART_InitTypeDef USART_InitStructure;
  USART_ClockInitTypeDef USART_ClockInitStructure;
 
  USART_StructInit(&USART_InitStructure);//使用默认初始设置
  USART_ClockStructInit(&USART_ClockInitStructure);//使用默认的初始设置
 
  USART_Init(USART1,&USART_InitStructure);
  USART_ClockInit(USART1,&USART_ClockInitStructure);
  USART_Cmd(USART1,ENABLE);
 
  //接收和发送中断使能打开
  USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);
  USART_ITConfig(USART1,USART_IT_TXE,ENABLE);
}

void USART1_IRQHandler()
{
  if(USART_GetITStatus(USART1,USART_IT_RXNE)!=RESET){
    USART_ITConfig(USART1,USART_IT_RXNE,DISABLE);
  }
  if(USART_GetITStatus(USART1,USART_IT_TXE)!=RESET){
    USART_SendData(USART1,*(SendData++));
    if(*(SendData)=='\0')
      USART_ITConfig(USART1,USART_IT_TXE,DISABLE);
  }
}

void print(char *p)
{
  SendData=p;
  USART_ITConfig(USART1,USART_IT_TXE,ENABLE);
  while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
}
/**
  * @brief  Main program.
  * @param  None
  * @retval : None
  */
int main(void)
{
  /* Setup STM32 system (clock, PLL and Flash configuration) */
  SystemInit();

  /* Add your application code here
     */
 
  RCC_Config();
  GPIO_Config();
  NVIC_Config();
  USART_Config();

  /* Infinite loop */
  while (1)
  { 
    print("Hello\r\n");
//    while(USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET);
  }
}

#ifdef  USE_FULL_ASSERT

/**
  * @brief  Reports the name of the source file and the source line number
  *   where the assert_param error has occurred.
  * @param file: pointer to the source file name
  * @param line: assert_param error line source number
  * @retval : None
  */
void assert_failed(uint8_t* file, uint32_t line)
{
  /* User can add his own implementation to report the file name and line number,
     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */

  /* Infinite loop */
  while (1)
  {
  }
}
#endif

/**
  * @}
  */

/******************* (C) COPYRIGHT 2009 STMicroelectronics *****END OF FILE****/

附件是整个工程：

USART.zip