The following is a tech note published by Microsoft, regarding a solution to accessing com ports above Com 9.

 

HOWTO: Specify Serial Ports Larger than COM9Last reviewed: January 20, 1997Article ID: Q115831

The information in this article applies to: Microsoft Win32 Application Programming Interface (API) included with: - Microsoft Windows NT versions 3.1, 3.5, 3.51, 4.0 - Microsoft Windows 95 version 4.0

CreateFile() can be used to get a handle to a serial port. The "Win32 Programmer's Reference" entry for "CreateFile()" mentions that the share mode must be 0, the create parameter must be OPEN_EXISTING, and the template must be NULL.

CreateFile() is successful when you use "COM1" through "COM9" for the name of the file; however, the message "INVALID_HANDLE_VALUE" is returned if you use "COM10" or greater.

If the name of the port is //./COM10, the correct way to specify the serial port in a call to CreateFile() is as follows:

CreateFile( ".//COM10", // address of name of the communications device fdwAccess, // access (read-write) mode 0, // share mode NULL, // address of security descriptor OPEN_EXISTING, // how to create 0, // file attributes NULL // handle of file with attributes to copy );

NOTES: This syntax also works for ports COM1 through COM9. Certain boards will let you choose the port names yourself. This syntax works for those names as well.

Additional reference words: 3.10 3.50 4.00 95KBCategory: kbprg kbhowtoKBSubcategory: BseCommapi