EscapeCommFunction

The EscapeCommFunction function directs a specified communications device to perform an extended function.

BOOL EscapeCommFunction(
  HANDLE hFile,  // handle to communications device
  DWORD dwFunc   // extended function to perform
);
 

Parameters

hFile

Handle to the communications device. The CreateFile function returns this handle.

dwFunc

Specifies the code of the extended function to perform. This parameter can be one of the following values:

Value	Meaning
CLRDTR	Clears the DTR (data-terminal-ready) signal.
CLRRTS	Clears the RTS (request-to-send) signal.
SETDTR	Sends the DTR (data-terminal-ready) signal.
SETRTS	Sends the RTS (request-to-send) signal.
SETXOFF	Causes transmission to act as if an XOFF character has been received.
SETXON	Causes transmission to act as if an XON character has been received.
SETBREAK	Suspends character transmission and places the transmission line in a break state until the ClearCommBreak function is called (or EscapeCommFunction is called with the CLRBREAK extended function code). The SETBREAK extended function code is identical to the SetCommBreak function. Note that this extended function does not flush data that has not been transmitted.
CLRBREAK	Restores character transmission and places the transmission line in a nonbreak state. The CLRBREAK extended function code is identical to the ClearCommBreak function.

Return Values

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

Windows CE: Windows CE supports the following additional flags for the dwFunc parameter:

SETIR

Sets the serial port in IR mode.

CLRIR

Sets port into normal serial mode.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Requires version 1.0 or later.
  Header: Declared in winbase.h.
  Import Library: Use kernel32.lib.

See Also

Communications Overview, Communication Functions, ClearCommBreak, CreateFile, SetCommBreak