问题描述

VS2013 C++串口编程，接收刷卡器数据，调试显示字符串中的字符无效

C++代码：
hcom = CreateFile(_T("COM3"), GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING
, FILE_ATTRIBUTE_NORMAL, NULL);
if (hcom == INVALID_HANDLE_VALUE)
{
return;
}
SetupComm(hcom, 1024, 1024);
COMMTIMEOUTS TimeOuts;
//设定读超时
TimeOuts.ReadIntervalTimeout = 1000;
TimeOuts.ReadTotalTimeoutMultiplier = 5;
TimeOuts.ReadTotalTimeoutConstant = 50;
//设定写超时
TimeOuts.WriteTotalTimeoutMultiplier = 500;
TimeOuts.WriteTotalTimeoutConstant = 2000;
SetCommTimeouts(hcom, &TimeOuts); //设置超时
DCB dcb;
GetCommState(hcom, &dcb);
dcb.BaudRate = 9600;
dcb.ByteSize = 8;
dcb.Parity = NOPARITY;
dcb.StopBits = TWOSTOPBITS;
SetCommState(hcom, &dcb);
PurgeComm(hcom, PURGE_TXCLEAR | PURGE_RXCLEAR);
char str[100];
DWORD wCount=0;//读取的字节数
BOOL bReadStat=false;
bReadStat = ReadFile(hcom, str, 100, &wCount, NULL);
if (!bReadStat)
{
MessageBox(_T("读串口失败!"));
return;
}
调试图片：

解决方案

你试试我用的

static HANDLE hCom = NULL;
static OVERLAPPED m_osRead;
static OVERLAPPED m_osWrite;
static DCB dcb;

#define BAUD_RATE 9600

int com_open( int comindex )
{
char comname[8];

memset(comname,0, sizeof(comname));
sprintf(comname,"COM%d", comindex);

hCom = CreateFileA(comname, GENERIC_READ|GENERIC_WRITE, //允许读写
    0,                      //值必须为０，表示不将串口与其他应用程序共享
    NULL,                   // no security attrs
    OPEN_EXISTING,          // 指定如何打开文件，在打开设备（串口是一种设备）时，此参数必须指定为ＯＰＥＮ＿ＥＸＩＳＴＩＮＧ
    FILE_ATTRIBUTE_NORMAL|FILE_FLAG_OVERLAPPED, //指定文件属性及相关标志，但是对于串行口，唯一有意义的设置是ＦＩＬＥ＿ＦＬＡＧ＿ＯＶＥＲＬＡＰＰＥＤ或０
    NULL);
if( hCom ==  (HANDLE)-1 )
{
    return 0;
}
GetCommState(hCom, &dcb );  //读串口原来的参数设置
dcb.BaudRate = BAUD_RATE;
dcb.ByteSize = 8;
dcb.Parity = NOPARITY;
dcb.StopBits = ONESTOPBIT ;
dcb.fBinary = TRUE;
dcb.fParity = FALSE;
SetCommState( hCom, &dcb ); //串口参数配置
SetCommMask(hCom, EV_RXCHAR|EV_TXEMPTY );//设置事件驱动的类型
SetupComm( hCom, 1024,1024) ; //设置输入、输出缓冲区的大小
PurgeComm( hCom, PURGE_TXABORT | PURGE_RXABORT |PURGE_TXCLEAR|PURGE_RXCLEAR);//清干净输入、输出缓冲区 

COMMTIMEOUTS TimeOuts;
//设置读超时
TimeOuts.ReadIntervalTimeout=1;
TimeOuts.ReadTotalTimeoutMultiplier=1;
TimeOuts.ReadTotalTimeoutConstant=1;
//设置写超时
TimeOuts.WriteTotalTimeoutMultiplier=1;
TimeOuts.WriteTotalTimeoutConstant=1;
SetCommTimeouts(hCom,&TimeOuts); //设置超时

memset(&m_osRead,0,sizeof(OVERLAPPED));
m_osRead.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);

memset(&m_osWrite,0,sizeof(OVERLAPPED));
m_osWrite.hEvent=CreateEvent(NULL,TRUE,FALSE,NULL);

//check
bool ret = CheckConnect(300);
if( ret <= 0 )
{
    CloseHandle(hCom);
    hCom = NULL;
    return 0;
}

return 1;

}

int ReceiveData( unsigned char *buff_Receive )
{
COMSTAT ComStat;
DWORD dwErrorFlags;

DWORD dwBytesRead=1024;//读取的字节数
BOOL bReadStat=FALSE;

ClearCommError(hCom,&dwErrorFlags,&ComStat);

if(!ComStat.cbInQue)
    return 0;
dwBytesRead=min(dwBytesRead,(DWORD)ComStat.cbInQue);
bReadStat=ReadFile(hCom,buff_Receive,dwBytesRead,&dwBytesRead,&m_osRead);
if(!bReadStat)
{
    if(GetLastError()==ERROR_IO_PENDING)
        //GetLastError()函数返回ERROR_IO_PENDING,表明串口正在进行读操作
    {
        WaitForSingleObject(m_osRead.hEvent,10);
        //使用WaitForSingleObject函数等待，直到读操作完成或延时已达到2秒钟
        //当串口读操作进行完毕后，m_osRead的hEvent事件会变为有信号
    }
}

// PurgeComm(hCom, PURGE_TXABORT|PURGE_RXABORT|PURGE_TXCLEAR|PURGE_RXCLEAR);
return dwBytesRead;

}

解决方案二：

com_open中的CheckConnect可以直接去掉