当我尝试与TTI设备通讯时，C ++无法通过ReadFile / WriteFile接收数据

Question

我来找您是因为尝试编写支持TTI的QL355P的驱动程序时遇到了一些问题。 我已经用VB6编写了驱动程序，但是现在，我试图用C ++编写它。 我使用ReadFile / WriteFile函数与接口进行通信。 问题是当我发送识别命令（* IDN？）和endchar（。）时，我没有响应（我有Statut_timeout）。

我的代码是：

DCB l_dcb;
BOOL l_Success;
 COMMTIMEOUTS l_TimeOuts;
 const char *command = "*IDN?.";
 // open an access to serial port
 m_ComPort = CreateFile(L"COM2",
  GENERIC_READ | GENERIC_WRITE,
  0,    // comm devices must be opened w/exclusive-access
  NULL, // no security attrs
  OPEN_EXISTING, // comm devices must use OPEN_EXISTING
  0,    // not overlapped I/O
  NULL  // hTemplate must be NULL for comm devices
  );

 // get the current configuration
 l_Success = GetCommState(m_ComPort, &l_dcb);

 // fill in the DCB with configuation:
// baud=19200, 8 data bits, no parity, 1 stop bit
l_dcb.BaudRate = 19200;
l_dcb.ByteSize = 8;
l_dcb.Parity = NOPARITY;
l_dcb.StopBits = ONESTOPBIT;

// configure the port
l_Success = SetCommState(m_ComPort, &l_dcb);

// get the current time-outs configuration
l_Success = GetCommTimeouts(m_ComPort, &l_TimeOuts);

 // change the time-outs
l_TimeOuts.ReadIntervalTimeout=50;
l_TimeOuts.ReadTotalTimeoutMultiplier=50;
l_TimeOuts.ReadTotalTimeoutConstant=1000;

// sets the time-outs configuration
l_Success = SetCommTimeouts(m_ComPort, &l_TimeOuts);

// first purge the input buffer
PurgeComm(m_ComPort,PURGE_RXCLEAR);

// send the command
DWORD l_NumBytesTransfered=0;
DWORD l_NumBytesToTransfer=strlen(command);
l_Success = WriteFile(m_ComPort,command,l_NumBytesToTransfer,&l_NumBytesTransfered,NULL);

//Try to read
char l_Char='*';
int i=0;
char l_Pointer[100];
while(l_Char !=0x0a && i<100)
{
    l_Success = ReadFile(m_ComPort,&l_Char,1,&l_NumBytesTransfered,NULL);

    l_Pointer[i] = l_Char;
    i++;
}
CloseHandle(m_ComPort); //close the handle

Answer 1

如果发生超时或各种可能的错误，ReadFile可以返回0。 您的代码段忽略了这种可能性，即使ReadFile失败，也会将垃圾放入输入数组。