串口通信实验计划：

配置初始化串口1，使用串口1周期性发送数据给上位机。

串口通信配置代码：

#include "stdarg.h"      //自定义printf需要使用
#include "stdio.h"       //1.61328125kb
#include "USART1.h"

#include "USART1.h"

#define USART_REC_LEN 30

u8 USART_RX_BUF[USART_REC_LEN] __attribute__ ((at(0X20001000)));
//接收缓冲,最大USART_REC_LEN个字节,起始地址为0X20001000.
u16 USART_RX_STA=0;       //接收状态标记	 
u16 USART_RX_CNT=0;			//接收的字节数	 


#if 1  
#pragma import(__use_no_semihosting)               
//标准库需要的支持函数                   
struct __FILE   
{   
    int handle;   
    /* Whatever you require here. If the only file you are using is */   
    /* standard output using printf() for debugging, no file handling */   
    /* is required. */   
};   
/* FILE is typedef’ d in stdio.h. */   
FILE __stdout;         
//定义_sys_exit()以避免使用半主机模式      
void _sys_exit(int x)   
{   
    x = x;   
}   
//重定向fputc函数  
//printf的输出，指向fputc，由fputc输出到串口  
//这里使用串口1(USART1)输出printf信息  
int fputc(int ch, FILE *f)  
{        
    while((USART1->SR&0X40)==0);//循环发送,直到发送完毕   
    USART1->DR = (u8) ch; 
    return ch;  
}  
#endif

void uart1_init(u32 bound){
  //GPIO端口设置（初始化）
    GPIO_InitTypeDef GPIO_InitStructure;
	USART_InitTypeDef USART_InitStructure;
	NVIC_InitTypeDef NVIC_InitStructure;
	 
	RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE);	
	//使能USART1，GPIOA时钟
  
	//USART1_TX   GPIOA.9
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; //PA.9
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;	//复用推挽输出
  GPIO_Init(GPIOA, &GPIO_InitStructure);//初始化GPIOA.9
   
  //USART1_RX	  GPIOA.10初始化
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;//PA10
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;//浮空输入
  GPIO_Init(GPIOA, &GPIO_InitStructure);//初始化GPIOA.10  

  //Usart1 NVIC 配置
    NVIC_InitStructure.NVIC_IRQChannel = 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通道使能
	NVIC_Init(&NVIC_InitStructure);	//根据指定的参数初始化VIC寄存器
  
   //USART 初始化设置

	USART_InitStructure.USART_BaudRate = bound;//串口波特率
	USART_InitStructure.USART_WordLength = USART_WordLength_8b;//字长为8位数据格式
	USART_InitStructure.USART_StopBits = USART_StopBits_1;//一个停止位
	USART_InitStructure.USART_Parity = USART_Parity_No;//无奇偶校验位
	USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//无硬件数据流控制
	USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;	//收发模式

  USART_Init(USART1, &USART_InitStructure); //初始化串口1
  USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);//开启串口接受中断
  USART_Cmd(USART1, ENABLE);                    //使能串口1 

}

#ifndef _USART1_H_
#define _USART1_H_

#include "headfire.h"


void uart1_init(u32 bound);

#endif



int main(void)
{
	uint16_t t;
	
	delay_init();
	NVIC_Configuration();
	uart1_init(115200);
	printf("welcome!\r\n");
	
	
	while(1)
	{
		printf("%d\r\n",t);
		t++;
		delay_ms(500);

	}
}