STM32F103C6 USART1串口功能

基于STM32F103C6工程实现串口USART1功能，USART1串口TX为PA9,RX为PA10,配置一个USART1串口分为以下几步：

1. 初时化IO配置

2. 初时化USART NVIC配置

3. 初时化USART参数

4. 实现中断函数USART1_IRQHandler

5. 实现串口发送函数USART1_Send_Data

6. 主函数调用相关配置函数

Step 1: 初时化IO配置,初时化USART NVIC配置,初时化USART参数封装成一个函数

          Usart1_Init

#include "stm32f10x_usart.h"
#include "stm32f10x.h"
#include <stdio.h>

uint8_t rxBuf[40];
uint8_t rxLen;

/**
  * @brief  USART1串口初时化
  *        
  *         
  * @param  uint32_t baudrate[in]:设置波特率
  * @retval None
  */
void Usart1_Init(uint32_t baudrate)
{
	GPIO_InitTypeDef GPIO_InitStructure;
	USART_InitTypeDef USART_InitStructure;
	NVIC_InitTypeDef NVIC_InitStructure;
	
	/* 初时化串口前，先将相应的时钟打开 */
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA,ENABLE);
	
	/* 初时化USART1 TX PA9引脚设为复用推挽输出 */
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;    
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_Init(GPIOA,&GPIO_InitStructure);
	
	/* 初时化USART1 RX PA10引脚为浮空输入 */
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
	GPIO_Init(GPIOA,&GPIO_InitStructure);
	
	
	/* USART1 NVIC初时化 */
	NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2); /*!< 设置NVIC中断分组2:2位抢占优先级，2位响应优先级   0-3; */
	NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn; /*!< USART1中断通道USART1_IRQn  */
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 3; /*!< 抢占优先级3 */
	NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;    /*!< 子优先级3 */
	NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;  /*!<  IRQ使能通道 */
	NVIC_Init(&NVIC_InitStructure);   /*!< 初时化NVIC寄存器  */
	
	/* USART初时化设置 */
	USART_InitStructure.USART_BaudRate = baudrate;   /*!<  设置波特率 */
	USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
	USART_InitStructure.USART_WordLength = USART_WordLength_8b; /*!< 8位数据*/
	USART_InitStructure.USART_StopBits = USART_StopBits_1;   /*!< 1位停止位 */
	USART_InitStructure.USART_Parity = USART_Parity_No;   /*!< 无校验位 */
	USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;  /*!< 收发模式*/
	USART_Init(USART1,&USART_InitStructure);  /*!< 初时化串口1 */
	
	/* 开启串口1接收中断 */
	USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);
	/* 使能串口1 */
	USART_Cmd(USART1,ENABLE);

}

Step 2: 实现中断函数USART1_IRQHandler

/**
  * @brief  USART1串口中断函数
  *        
  *         
  * @param  None
  * @retval None
  */
void USART1_IRQHandler(void) 
{
	/* 暂存接收结果 */
	uint8_t result;
  /* @note
  *   - PE (Parity error), FE (Framing error), NE (Noise error), ORE (OverRun 
  *     error) and IDLE (Idle line detected) pending bits are cleared by 
  *     software sequence: a read operation to USART_SR register 
  *     (USART_GetITStatus()) followed by a read operation to USART_DR register 
  *     (USART_ReceiveData()).
  *   - RXNE pending bit can be also cleared by a read to the USART_DR register 
  *     (USART_ReceiveData()).
  */
	/* 检查是否为USART1接收中断 */
	if(USART_GetITStatus(USART1,USART_IT_RXNE) != RESET)
	{
		 result = USART_ReceiveData(USART1);   
                 if(rxLen < 20)
		 {
			 rxBuf[rxLen] = result;
			 rxLen++;
		 }			 
	}
	else
        {
            USART_ReceiveData(USART1);
	}
	
	
	

}

Step 3:实现串口发送函数USART1_Send_Data

/**
* @brief  USART1串口发送函数
  *        
  *         
	* @param   uint8_t *buf[in]:待发送的数据buffer
* @param   uint16_t len:发送的数据长度
  * @retval None
  */
void USART1_Send_Data(uint8_t *buf,uint16_t len)
{
	for(uint16_t i = 0; i<len; i++)
	{
  /*- TC pending bit can be also cleared by software sequence: a read 
  *     operation to USART_SR register (USART_GetITStatus()) followed by a write 
  *     operation to USART_DR register (USART_SendData()).
  *   - TXE pending bit is cleared only by a write to the USART_DR register 
  *     (USART_SendData()).
  */
		while(USART_GetFlagStatus(USART1,USART_FLAG_TC); /*!<发送是否完成*/
		USART_SendData(USART1,buf[i]);
	}	
}

 Step 4:主函数调用相关配置函数

/**
  * @brief  主函数，程序的入口
  *        
  *         
  * @param  None
  * @retval int:不用理会，对于嵌入式系统，永远都不会返回
  */
int main(void)
{
	Usart1_Init(9600);
	for(;;)
	{
		if(rxLen >= 20)
		{
			USART1_Send_Data(rxBuf,20);
			rxLen = 0;
		}
		
	}
}

串口功能完成，那么如何实现printf函数功能呢，重定义fputc函数

//重定义fputc函数 
int fputc(int ch, FILE *f)
{      
	while((USART1->SR&0X40)==0);
	USART1->DR = (u8) ch;      
		
	return ch;
}

此时还需要勾选Use MicroLib选项

另一种方法不需要勾选Use MicroLib选项，如下：

/* 加入以下代码,支持printf函数,而不需要选择use MicroLIB */
#ifdef DEBUG
#pragma import(__use_no_semihosting)             
//标准库需要的支持函数                 
struct __FILE 
{ 
	int handle; 

}; 

FILE __stdout;       
//定义_sys_exit()以避免使用半主机模式    
void _sys_exit(int x) 
{ 
	x = x; 
}  
//重定义fputc函数 
int fputc(int ch, FILE *f)
{      
	while((USART1->SR&0X40)==0);
	USART1->DR = (u8) ch;      
		
	return ch;
}
#endif 

断言功能实现，首先得定义宏USE_FULL_ASSERT打开断言功能，然后实现函

数assert_failed

#if USE_FULL_ASSERT
void assert_failed(uint8_t* file, uint32_t line)
{
	printf("\r\nfile path is %s,error line is %d\r\n",file,line);
	while(1);
}
#endif