RS232串口的Windows编程纪要

// 为了清晰结构，代码有删减，但能正常运行
//
#include "serialport.h"
#include<string.h>

int main(int argc, char* argv[])
{
    //定义两个句柄，用来报错打开后的两个串口相关资源信息
    //句柄是编程中常用的说法，通常都表示指向一堆数据的标志
    HANDLE h1,h2;
    //定义一个字符串，字符串的内容其实无所谓，用于演示串口通讯的内容
    char *msg="Hello, human!\n";
    //要传输的数据的长度
    int n=strlen(msg);
    //一个串口接受用的缓冲区，100是随意给出的，只要大于通讯对端一次传输的数据量即可
    char buf[100];

    //首先将接受缓冲区清空，在正常、确定长度的数据传输中，这一步并不必要
    //但在字符串传输的演示中，还是需要清空的，以保证在串味没有乱字符出现
    memset(buf,0,100);
    //给用户一个提示，表示传输测试开始了，因为至少以今天的眼光看，串口速度还是很慢的
    printf("Serial port test begin ...!\n");
    //打开并设置发送端串口，后面的串口编号是在设备管理器中查询到的
    //在正式的系统中，这个串口通常会由用户在参数设置中修改
    //Uart是英文中对串口的另外一个称呼，serial port/com也是同义
    SetupUart(&h1,"com7");
    //打开并设置接收端串口
    SetupUart2(&h2,"com8");
    //在发送端口写出数据，也就是我们准备的字符串
    //串口通讯可以容纳的内容范围很广，不仅是字符串，所以使用unsigned char类型
    WriteUart((unsigned char*)msg,n,h1);
    //在接受端口读取数据，注意因为接收是阻塞式的，所以读取的长度要<=发送的数据包长度，
    //否则会让程序阻塞在这里一直等待读取
    ReadUart((unsigned char*)buf,n,h2);
    //显示接收到的数据内容
    printf("Loop received:%s",buf);
    //关闭两个打开的串口
    CloseUart2();
    CloseUart();

    return 0;
}

//以下代码原型来自MSDN官方示例，为了保持原始代码的风格，尽量不做改动
//代码中有很多东西超出一般学习的范围，比如多线程的事件同步等，可以先大概了解即可
//对于不熟悉的代码，初期可以抄过来用，了解对外的API即可，有时间再去下功夫了解细节
#include "serialPort.h"

DCB            PortDCB; 
COMMTIMEOUTS   CommTimeouts; 
HANDLE         hPort1,hPort2;
char           lastError[1024];

//以下是一些端口设置使用的常量，在正常项目中应当也是归集于配置系统中的
//串口顾名思义是将数据串流化通讯，因此需要定义发送、接收方都完全相同的速度、位长、校验模式等
//另外因为我们只用了三根数据线，其它控制位的设置我们就省略掉了
//这些常量参数使用index*这样的方式是为了同传统界面上的各项设置做的对应，变量命名嘛，不用过于纠结。
int index1=4,//9600
    index2=3,//8
    index3=2,//NOPARITY
    index4=0,//ONSTOPBIT
    index5=-1;
//打开并且设置串口
int SetupUart(HANDLE *hPort,char *port1)
{
    //打开串行端口，也是把端口当做一个文件来对待
    //对于新手，为什么用这个函数之类的问题，只能先死记了
    hPort1 = CreateFile (TEXT(port1),                       // Name of the port 
                        GENERIC_READ | GENERIC_WRITE,     // Access (read-write) mode 
                        0,                                  
                        NULL,                             
                        OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL,                     
                        NULL);                             
             
    //打开失败就报个警并退出后续操作
    if ( hPort1 == INVALID_HANDLE_VALUE )
    { 
        MessageBox (NULL, "Port Open Failed" ,"Error", MB_OK);
        return 0;
    }   
    *hPort = hPort1;
      //读取当前串口的状态
      PortDCB.DCBlength = sizeof (DCB); 
      GetCommState (hPort1, &PortDCB);
      //在当前串口状态的基础上设置串口速率等参数
      configure();

      //读取当前超时设置
      GetCommTimeouts (hPort1, &CommTimeouts); 
      //根据当前超时设置，设置自己期望的值
      configuretimeout();
    
   

    //Re-configure the port with the new DCB structure. 
    //上面的configure只是设置了参数结构，下面函数才是真正将之设置到串口
    if (!SetCommState (hPort1, &PortDCB)) 
    { 
        MessageBox (NULL, "1.Could not create the read thread.(SetCommState Failed)" ,"Error", MB_OK);
        CloseHandle(hPort1);   
        return 0; 
     } 

    // Set the time-out parameters for all read and write operations on the port. 
    //同样设置configuretimeout输出的结果
    if (!SetCommTimeouts (hPort1, &CommTimeouts)) 
    { 
        MessageBox (NULL, "Could not create the read thread.(SetCommTimeouts Failed)" ,"Error", MB_OK);
        CloseHandle(hPort1);  
        return 0; 
    } 

    // Clear the port of any existing data. 
    //如果串口还有以前通讯积累的未完结数据，清理掉
    if(PurgeComm(hPort1, PURGE_TXCLEAR | PURGE_RXCLEAR)==0) 
    {   MessageBox (NULL, "Clearing The Port Failed" ,"Message", MB_OK);
        CloseHandle(hPort1); 
        return 0; 
    } 
    
    //MessageBox (NULL, "Port1 SETUP OK." ,"Message", MB_OK);
    return 1;
}
//下面函数功能同上面的完全一样，其实设置一个函数就好，这里保持原状
int SetupUart2(HANDLE *hPort,char *port2)
{
    //int STOPBITS;

    hPort2 = CreateFile (TEXT(port2),                      // Name of the port 
                        GENERIC_READ | GENERIC_WRITE,     // Access (read-write) mode 
                        0,                                  
                        NULL,                             
                        OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL,                     
                        NULL);                             
             
    if ( hPort2 == INVALID_HANDLE_VALUE ) 
    { 
        
        MessageBox (NULL, "Port Open Failed" ,"Error", MB_OK);
        return 0;
    }
    *hPort = hPort2;
    
     // Initialize the DCBlength member. 
     PortDCB.DCBlength = sizeof (DCB); 
      
      // Get the default port setting information.
      GetCommState (hPort2, &PortDCB);
      configure();

      // Retrieve the time-out parameters for all read and write operations  
    GetCommTimeouts (hPort2, &CommTimeouts);
    configuretimeout();

    //Re-configure the port with the new DCB structure. 
    if (!SetCommState (hPort2, &PortDCB)) 
    { 
        MessageBox (NULL, "1.Could not create the read thread.(SetCommState Failed)" ,"Error", MB_OK);
        CloseHandle(hPort2);   
        return 0; 
     } 
    
    // Set the time-out parameters for all read and write operations on the port. 
    if (!SetCommTimeouts (hPort2, &CommTimeouts)) 
    { 
        MessageBox (NULL, "Could not create the read thread.(SetCommTimeouts Failed)" ,"Error", MB_OK);
        CloseHandle(hPort2);  
        return 0; 
    } 

    // Clear the port of any existing data. 
    if(PurgeComm(hPort2, PURGE_TXCLEAR | PURGE_RXCLEAR)==0) 
    {   MessageBox (NULL, "Clearing The Port Failed" ,"Message", MB_OK);
        CloseHandle(hPort2); 
        return 0; 
    } 
    
    //MessageBox (NULL, "Port2 SETUP OK." ,"Message", MB_OK);
    return 1;
}


//PortDCB是全局变量，这里根据读取到的端口状态，设置自己希望的通讯参数
int configure()
{
    // Change the DCB structure settings
    PortDCB.fBinary = TRUE;                         // Binary mode; no EOF check
    PortDCB.fParity = TRUE;                         // Enable parity checking 
    PortDCB.fDsrSensitivity = FALSE;                // DSR sensitivity 
    PortDCB.fErrorChar = FALSE;                     // Disable error replacement 
    PortDCB.fOutxDsrFlow = FALSE;                   // No DSR output flow control 
    PortDCB.fAbortOnError = FALSE;                  // Do not abort reads/writes on error
    PortDCB.fNull = FALSE;                          // Disable null stripping 
    PortDCB.fTXContinueOnXoff = TRUE;                // XOFF continues Tx 
    //设置波特率
    switch(index1)                                  // BAUD Rate
        {
        case 0:
            PortDCB.BaudRate= 115200;            
        break;
        case 1:
            PortDCB.BaudRate = 19200;            
        break;
        case 2:
            PortDCB.BaudRate= 38400;            
        break;
        case 3:
             PortDCB.BaudRate = 57600;            
        break;
        case 4:
             PortDCB.BaudRate = 9600;            
        break;
        default:
            break;
        }
        //设置通讯字节位长
        switch(index2)                                     // Number of bits/byte, 5-8 
        {
        case 0:
            PortDCB.ByteSize = 5;            
        break;
        case 1:
            PortDCB.ByteSize = 6;            
        break;
        case 2:
            PortDCB.ByteSize= 7;            
        break;
        case 3:
            PortDCB.ByteSize=8;            
        break;
        default:
            break;
        }
        //校验方式
        switch(index3)                                     // 0-4=no,odd,even,mark,space 
        {
        case 0:
            PortDCB.Parity= EVENPARITY;                
        break;
        case 1:
             PortDCB.Parity = MARKPARITY;               
        break;
        case 2:
              PortDCB.Parity = NOPARITY;                   
        break;
        case 3:
             PortDCB.Parity = ODDPARITY;           
        break;
        case 4:
             PortDCB.Parity = SPACEPARITY;           
        break;
        default:
            break;
        }
        //停止位
        switch(index4)                       
        {
        case 0:
            PortDCB.StopBits =  ONESTOPBIT;          
        break;
        case 1:
            PortDCB.StopBits =  TWOSTOPBITS;        
        break;
        
        default:
            break;
        }
        //是否使用硬件流控制等
        switch(index5)                       
        {
        case 0:
            PortDCB.fOutxCtsFlow = TRUE;                        // CTS output flow control 
            PortDCB.fDtrControl = DTR_CONTROL_ENABLE;           // DTR flow control type 
            PortDCB.fOutX = FALSE;                              // No XON/XOFF out flow control 
            PortDCB.fInX = FALSE;                               // No XON/XOFF in flow control 
            PortDCB.fRtsControl = RTS_CONTROL_ENABLE;           // RTS flow control 
             
            
        break;
        case 1:
            PortDCB.fOutxCtsFlow = FALSE;                      // No CTS output flow control 
            PortDCB.fDtrControl = DTR_CONTROL_ENABLE;          // DTR flow control type 
            PortDCB.fOutX = FALSE;                             // No XON/XOFF out flow control 
            PortDCB.fInX = FALSE;                              // No XON/XOFF in flow control 
            PortDCB.fRtsControl = RTS_CONTROL_ENABLE;          // RTS flow control 
        break;
        case 2:
            PortDCB.fOutxCtsFlow = FALSE;                      // No CTS output flow control 
            PortDCB.fDtrControl = DTR_CONTROL_ENABLE;          // DTR flow control type 
            PortDCB.fOutX = TRUE;                              // Enable XON/XOFF out flow control 
            PortDCB.fInX = TRUE;                               // Enable XON/XOFF in flow control 
            PortDCB.fRtsControl = RTS_CONTROL_ENABLE;          // RTS flow control 
        break;
        
        default:
            break;
        }

    return 1;
}
int configuretimeout()
{   //超时设置，放置读写端口时时间过长程序挂起
    //memset(&CommTimeouts, 0x00, sizeof(CommTimeouts)); 
    CommTimeouts.ReadIntervalTimeout = 50; 
    CommTimeouts.ReadTotalTimeoutConstant = 50; 
    CommTimeouts.ReadTotalTimeoutMultiplier=10;
    CommTimeouts.WriteTotalTimeoutMultiplier=10;
    CommTimeouts.WriteTotalTimeoutConstant = 50; 
   return 1;
}
int WriteUart(unsigned char *buf1, int len,HANDLE hPort)
{
    DWORD dwNumBytesWritten;
    //使用写文件的方式向串口输出数据
    //因为串口芯片及驱动程序都有缓存，所以一般小数据量的写出都不会阻塞
    WriteFile (hPort,buf1, len,&dwNumBytesWritten,NULL);            

    if(dwNumBytesWritten > 0)
    {
        //MessageBox (NULL, "Transmission Success" ,"Success", MB_OK);
        return 1;
    }
    
    else 
       {
        MessageBox (NULL, "Transmission Failed" ,"Error", MB_OK);
        return 0;   
       }
}


int ReadUart(unsigned char *buf2,int len,HANDLE hPort)
{
    //BOOL ret;
    DWORD dwRead;
    BOOL fWaitingOnRead = FALSE;
    OVERLAPPED osReader = {0};
    unsigned long retlen=0;

   // Create the overlapped event. Must be closed before exiting to avoid a handle leak.
    //读取串口的时候，如果对方尚未发送指定长度的数据，会导致读取串口阻塞
    //这里使用线程同步的事件响应方式，防止读取数据阻塞
    //所以读取串口可能返回0表示没有读取到数据
    //或者小于期望读取的字节表示数据尚未完全到来
   osReader.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
   if (osReader.hEvent == NULL)
       MessageBox (NULL, "Error in creating Overlapped event" ,"Error", MB_OK);
   if (!fWaitingOnRead)
   {
        //具体的读取数据
          if (!ReadFile(hPort, buf2, len, &dwRead,  &osReader)) 
          {
          FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                        NULL,
                        GetLastError(),
                        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                        lastError,
                        1024,
                        NULL);
           MessageBox (NULL, lastError ,"MESSAGE", MB_OK);
           }
           else
           {
             // MessageBox (NULL, "ReadFile Suceess" ,"Success", MB_OK);
           }
    }
    
    if(dwRead > 0)  
    {
        //MessageBox (NULL, "Read DATA Success" ,"Success", MB_OK);//If we have data
        return (int) retlen;
    }
         //return the length
    
    else return 0;     //else no data has been read
 }

//关闭端口，同样有一个就够了
int CloseUart()
{
    CloseHandle(hPort1); 
    return 1;
}
int CloseUart2()
{
    CloseHandle(hPort2);
    return 1;
}