单片机实现点对点的数据传输-串口通讯

单片机在控制本地的外围期间时，信息的交互是通过8位并行数据总线进行的，但是在较大规模的现代控制系统中，单片机还需要控制远端的设备，可以利用单片机的串行通信模块，在学习了RS-232串口通信的原理和时序后，学习了利用RS-232接口实现串口数据传输的点对点通信。

 

主要器件：

1、  AT89C52单片机芯片，用于控制串口通信。

2、  接口电平转换芯片MAX3232，用于实现TTL电平和RS-232电平的转换。

 

试验流程图：主机部分                             

 从机部分:

试验电路图：

试验程序代码：

//PPDataR.h程序

#ifndef       _PPDATAR_H         // 防止PPDataT.h被重复引用

 

#define       _PPDATAR_H

 

#include

#include

 

#define uchar unsigned char

#define uint unsigned int

 

/* 握手信号宏定义 */

#define CALL 0x24              // 主机呼叫

#define BUSY 0x15              // 从机忙

#define OK 0x00                     // 从机准备好

#define SUCC 0x2A              // 接收成功

#define ERR 0xF0              // 接收错误

 

#define MAXLEN 64           // 缓冲区最大长度

 

uchar buf[MAXLEN];

 

#endif

 

//PPDataR.c程序

#include 'PPDataR.h'

 

/* 发送数据函数 */

uchar recvdata(uchar *buf)

{

       uchar i,tmp;

       uchar len;                                   // 保存数据长度

       uchar ecc;                                   // 保存校验字节

      

       /* 接收数据长度字节 */

       RI = 0;

       while(!RI);

       len = SBUF;

       RI = 0;

      

       /* 使用len的值为校验字节ecc赋初值 */

       ecc = len;                                  

 

       /* 接收数据 */

       for (i=0;i

       {

              while(!RI);

              *buf = SBUF;    

              ecc = ecc^(*buf);            // 进行字节校验

              RI = 0;      

              buf++;             

       }

       *buf = 0;                             // 表示数据结束

      

       /* 接收校验字节 */

       while(!RI);

       tmp = SBUF;

       RI = 0;

 

       /* 进行数据校验 */

       ecc = tmp^ecc;

       if (ecc!=0)                                   // 如果校验错误

       {

              *(buf-len) = 0;                  // 清空数据缓冲区

             

              /* 发送校验错误信号ERR */

              TI = 0;      

              SBUF = ERR;

              while(!TI);

              TI = 0;

 

              return 0xff;                     // 返回0xff表示校验错误

       }

 

       /* 发送校验成功信号SUCC */

       TI = 0;

       SBUF = SUCC;

       while(!TI);

       TI = 0;

 

       return 0;                              // 校验成功，返回0

}

 

void init_serial()

{

       TMOD = 0x20;                           // 定时器T1使用工作方式2

       TH1 = 250;

       TL1 = 250;

       TR1 = 1;                             // 开始计时

       PCON = 0x80;                           // SMOD = 1

       SCON = 0x50;                           // 工作方式1，波特率9600kbit/s，允许接收

}

 

/* 主程序 */

void main()

{

       uchar tmp = 0;

       /* 串口初始化 */

       init_serial();

 

       EA = 0;                               // 关闭所有中断

 

       while(1)

       {

              /* 如果接收到的数据不是CALL，则继续等待 */

              while (tmp!=CALL)

              {

                     RI = 0;

                     while(!RI)

                     tmp = SBUF;

                     RI = 0;

              }

      

              /* 检测P0口判断当前是否工作忙，若P0＝0xBB，则为忙状态 */

              P0 = 0xff;

              tmp = P0;

              if(tmp==0xBB)         // 如果P0口为0xBB，发送BUSY信号

              {

                     TI = 0;

                     SBUF = BUSY;

                     while(!TI);

                     TI = 0;

                     continue;

              }

 

              /* 否则发送OK信号，表示从机可以接收数据 */

              TI = 0;                           

              SBUF = OK;

              while(!TI);

              TI = 0;

 

              /* 数据接收 */

              tmp = 0xff;

              while(tmp==0xff)

              {

                     tmp = recvdata(buf); // 校验失败返回0xff，接收成功返回0

              }

       }

}