Resetting a Serial Port's RTS and DTR Signals when Windows Starts
de Joe W4TV
You can reset a serial port's RTS and DTR signals on Windows startup by creating a Windows Batch File containing the appropriate command, and then creating a Window Shortcut to this Batch File in the Windows Startup Folder. To reset COM3's RTS and DTR signals, for example, use Windows Notepad to create a Batch File named RESETCOM3.bat that contains
MODE COM3: dtr=off rts=off
On Windows XP, the pathname of the Windows Startup Folder is
C:\Documents and Settings\%username%\Start Menu\Programs\Startup
where %username% is the username you used to log in to Windows.
On Windows 7, the pathname of the Windows Startup Folder is
To create the required Shortcut, run two instances of Windows Explorer. In the first instance, navigate to the folder in which you created RESETCOM3.bat; in the second instance, navigate to the Windows Startup Folder. Then depress-and-hold the ALT key while dragging RESETCOM3.bat from the first instance of Windows Explorer to the second; when you release the left mouse button, a shortcut to RESETCOM3.bat will appear in the Windows Startup Folder.