嵌入式学习笔记之UART编程练习

最新推荐文章于 2024-05-19 12:08:45 发布

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最新推荐文章于 2024-05-19 12:08:45 发布

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分类专栏：嵌入式学习文章标签：编程嵌入式 Linux UART通信协议

本文链接：https://blog.youkuaiyun.com/sui_yirufeng/article/details/8982037

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本文详细介绍了UART通信协议的基本原理，包括传输过程、寄存器设置等，并通过代码示例展示了如何实现UART数据的收发。重点突出了UART配置、初始化及发送接收字符的方法。

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#include <string.h>
#include <stdio.h>

#include "Target\44b.h"
#include "Target\44blib.h"
/********************************************/
//   ARMSYS实验七：异步串行口（UART)应用测试 
//   描述：UART数据收发程序                    
/********************************************/

static int UartNum=0;
void myUart_Init(int whichuart, int baud)//对Uart进行初始化，以所需要的波特率为输入参数
{
   if(whichuart==0)
   {
        UartNum=0;
        rUFCON0=0x0;    //不使用FIFO
        rUMCON0=0x0;   //不使用自动流控制
        rULCON0=0x3;   //不采用红外线传输模式，无奇偶校验位，1个停止位，8个数据位
        rUCON0=0x245;   //发送中断为电平方式，接收中断为边沿方式，禁止超时中断，允许产生错误状态中断，禁止回送模式，禁止中止信号，传输模式为中断请求模式，接收模式也为中断请求模式。
        rUBRDIV0 = ( (int)(MCLK/16./baud + 0.5) -1 ); //根据波特率计算UBRDIV0的值
    }
    else if(whichuart==1)
    {
        UartNum=1;
        rUFCON1=0x0;    
        rUMCON1=0x0;   
        rULCON1=0x3; 
        rUCON1=0x245; 
        rUBRDIV1 = ( (int)(MCLK/16./baud + 0.5) -1 );
    }
}

void myUart_SendByte(char ch)
{
    if (UartNum ==0)
    {
	if(ch=='\n')
	{
	    while(!(rUTRSTAT0 & 0x2));//等待，直到发送缓冲区为空
	    //Delay(10);	//超级中断的响应速度较慢 
	    WrUTXH0('\r');//发送回车符
	}
	while(!(rUTRSTAT0 & 0x2)); //等待，直到发送缓冲区为空
	Delay(10);
	WrUTXH0(ch);//发送字符
    }
    else
    {
	if(ch=='\n')
	{
	    while(!(rUTRSTAT1 & 0x2));
	    Delay(10);	//because the slow response of hyper_terminal 
	    rUTXH1='\r';
	}
	while(!(rUTRSTAT1 & 0x2));  //Wait until THR is empty.
	Delay(10);
	WrUTXH1(ch);
    }	
}	


void myUart_Send (char *str)
{
    myUart_Init(0,115200);
	while (*str)
	  myUart_SendByte(*str++);
}


void Main(void)
{
    char aa;
	
    Port_Init();
    Led_Display(0xf);
    Beep(0x1);
    myUart_Send("\n\n*************************************************************************");
    myUart_Send("\n*                            -UART test-                                *");
    myUart_Send("\n*                           Version 1.10                                *");    
    myUart_Send("\n*                     Email:rao_dali@263.net                            *");
    myUart_Send("\n*               UART0 Config--COM:115.2kbps,8Bit,NP,UART0               *");
    myUart_Send("\n*-----------------------------------------------------------------------*");
    Beep(0x0);
    Led_Display(0x0);
    while(1);
}

UART的传输过程主要是通过寄存器的各个引脚的设置来达到，详细原理参见博文：http://blog.youkuaiyun.com/woshixiongge/article/details/8977414

#include "2410lib.h"
/*********************************************************************************************
* name:		uart0_test
* func:		uart test function
* para:		none
* ret:		none
* modify:
* comment:		
*********************************************************************************************/
void uart0_test()
{
	char cInput[256];
	UINT8T ucInNo=0;
	char c;
	uart_init(0,115200,0); //define the baud rate
	uart_printf("\n UART0 Communication Test Example\n");	
	uart_printf(" Please input words, then press Enter:\n");
#ifdef BOARDTEST	
	sprintf(&cInput, "Type via UART0 to test.");
	print_lcd(195,170,0x1c,&cInput);	
#endif
	uart_printf(" ");
	g_nKeyPress = 1;
	while(g_nKeyPress==1)			// only for board test to exit
	{
		c=uart_getch();
		//uart_sendbyte(c);
		
		uart_printf("%c",c);
		if(c!='\r')
			cInput[ucInNo++]=c;
		else
		{
			cInput[ucInNo]='\0';
			break;
		}
	}
	delay(1000);	
	uart_printf(" \nThe words that you input are: %s\n",cInput);		
	uart_printf(" end.\n");
}

uart_init()的系统定义如下：

void uart_init(int nMainClk, int nBaud, int nChannel)
{
    int i;
    
    if(nMainClk == 0)
    nMainClk    = PCLK;
    
    switch (nChannel)
    {
    	case UART0: 
		rUFCON0 = 0x0;   //UART channel 0 FIFO control register, FIFO disable
		rUMCON0 = 0x0;   //UART chaneel 0 MODEM control register, AFC disable
		rULCON0 = 0x3;   //Line control register : Normal,No parity,1 stop,8 bits
		// [10]       [9]     [8]     [7]          [6]      [5]        [4]         [3:2]          [1:0]
		// Clock Sel, Tx Int, Rx Int, Rx Time Out, Rx err,  Loop-back, Send break, Transmit Mode, Receive Mode
		// 0          1       0,      0            1        0          0,          01             01
		// PCLK       Level   Pulse   Disable      Generate Normal     Normal      Interrupt or Polling
		rUCON0  = 0x245;							// Control register
		//rUBRDIV0=( (int)(nMainClk/16./nBaud) -1 );	// Baud rate divisior register 0
		rUBRDIV0=( (int)(nMainClk/16./nBaud+0.5) -1 );	// Baud rate divisior register 0    
		break;
			
	case UART1: 
		rUFCON1 = 0x0;   //UART channel 1 FIFO control register, FIFO disable
		rUMCON1 = 0x0;   //UART chaneel 1 MODEM control register, AFC disable
		rULCON1 = 0x3;
		rUCON1  = 0x245;
		rUBRDIV1=( (int)(nMainClk/16./nBaud) -1 );
		break;
			
    	case UART2: 
		rULCON2 = 0x3;
		rUCON2  = 0x245;
		rUBRDIV2=( (int)(nMainClk/16./nBaud) -1 );    
		rUFCON2 = 0x0;   //UART channel 2 FIFO control register, FIFO disable
		break;
			
	default:
		break;
	}

    for(i=0;i<100;i++);
    delay(0);
}

换汤不换药，UART通信协议的实现都是通过寄存器的各个引脚实现传输。更多原理参见博文：http://blog.youkuaiyun.com/woshixiongge/article/details/8977414