Program Win32 program, Read data from COM port buffer.

void OnOpencom()
{
DCB dcb;
DWORD dwReadStatId;
HANDLE hRead;
開啟COM port, Overlapped屬性准許檔案同時被讀/寫
// Step I.
ComDev = CreateFile( "COM7",
GENERIC_READ | GENERIC_WRITE,
0,
0,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
0 );
if(ComDev == INVALID_HANDLE_VALUE)
{
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Error! When open COM-PORT.");
}
else
{
設定 COM port 讀/寫 Buffer. 如果沒有設定 Buffer 大小，COM port 會使用先前所設定的。
// Step II.
if( !SetupComm(ComDev, MAX_READ_BUFFER, MAX_WRITE_BUFFER) )
{
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Setup COMM error!");
return;
}

設定讀/寫 Timing
// Step III.
COMMTIMEOUTS time_out = {0, 0, 0, 0, 0};
time_out.ReadIntervalTimeout = MAXDWORD;
//time_out.ReadTotalTimeoutMultiplier = MAXDWORD;
//time_out.ReadTotalTimeoutConstant = 50;
// 5s time_out.WriteTotalTimeoutConstant = 5000;
// 50ms //time_out.WriteTotalTimeoutMultiplier = 5;
if( !SetCommTimeouts(ComDev, &time_out) )
{
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Set COMM timeout error!");
return;
}

設定 COM port 屬性
// Step IV.
GetCommState(ComDev, &dcb);
dcb.BaudRate = CBR_57600;
dcb.ByteSize = 8; dcb.Parity = NOPARITY;
dcb.StopBits = ONESTOPBIT;
if( !SetCommState(ComDev, &dcb) )
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Set COMM State ERROR!");

產生一 Thread 執行讀取工作
hRead = CreateThread( NULL, 0, (LPTHREAD_START_ROUTINE)ReadProc, (LPVOID)this, 0, &dwReadStatId ); if(hRead == NULL)
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Error! CreateThread(Read)");
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Open COM-PORT Successfully!");
}
}

DWORD WINAPI ReadProc(LPVOID lpV)
{
DWORD dwRes, dwErr, dwLen;
CRMSDlg *p = (CRMSDlg*)lpV;
CString str; COMSTAT comstat;
osRead.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);

if( osRead.hEvent == NULL) {
// Error.
}
while(1)
{
ClearCommError(ComDev, &dwErr, &comstat);
dwLen = comstat.cbInQue;
if(!dwLen) {
Sleep(200);
continue;
}
if( !ReadFile(ComDev, lpBuf, dwLen, &dwLen, &osRead) )
{
if( GetLastError() != ERROR_IO_PENDING) {
p->
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Error");
}
else {
switch( WaitForSingleObject(osRead.hEvent, 1000) )
{
case WAIT_OBJECT_0:
if( GetOverlappedResult(ComDev, &osRead, &dwLen, FALSE) ) p->
GetDlgItem(IDC_MYTEXT)->
SetWindowText(lpBuf);
else
// Error. p->
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Error"); break;
case WAIT_TIMEOUT:
// Error. p->
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Error");
break;
default: // Error. p->
GetDlgItem(IDC_MYTEXT)->
SetWindowText("Error");
} // switch
}
}
else
p->GetDlgItem(IDC_MYTEXT)->
SetWindowText(lpBuf);
}
}