CreateFile() fails for CNCA0

[Jonathan Taylor]

With version 1.4.0.0 of com0com, the HyperTerminal test succeeds, but I get a failure when trying to open the port with CreateFile():

m_hComm = CreateFile("CNCA0", 
                    GENERIC_READ | GENERIC_WRITE,
                    0,
                    0,
                    OPEN_EXISTING,
                    FILE_FLAG_OVERLAPPED,
                    0);

GetLastError() returns ERROR_FILE_NOT_FOUND.

Should I be using a different device name (other than "CNCA0")?  I tried a few other variations.

Thanks

[Jonathan Taylor]

Excellent question, Jonathan ;>

With device names of this type, you need to prefix them with \\.\, as in:

\\.\CNCA0

[elbreton]

Hello !

I tried to use CreateFile as described in the ReadMe & here, but without being successful ...

HANDLE h = CreateFile(    (LPCWSTR)"\\\\.\\CNCA0",
                            GENERIC_READ | GENERIC_WRITE,
                            0,
                            NULL,
                            OPEN_EXISTING,
                            FILE_ATTRIBUTE_SYSTEM,
                            NULL
                        );

The test with the Hyperterminal is ok. I don't have so much knowledges about COM ports, and my google searches didn't get me any further ...

So ... Any tip to get a step ahead would be very welcome ;)

Thanks

J

[elbreton]

In case another one would forget about UNICODE / ANSI stuff ...

The answer is contained in the previous line.

[Vyacheslav Frolov]

> HANDLE h = CreateFile( (LPCWSTR)"\\\\.\\CNCA0",

Try to replace (LPCWSTR) by TEXT():

  TEXT("\\\\.\\CNCA0"),

> FILE_ATTRIBUTE_SYSTEM,

Why is it?