problem: cannot open COM port

scene: xDevice --(I2C)--> xDriver --(stream interface)--> OS --(file object)--> Application

xDriver provides stream interface for COM port driver to the OS, and the OS provides file objects of a COM port device to applications. The application obtains information from xDriver through file objects to the COM port.

for example: (sample code on application layer)

BOOL xDriver::Open()
{
m_Handle = CreateFile( _T("COM7:"),
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
0,
NULL);

if(m_Handle == INVALID_HANDLE_VALUE) return FALSE;
return TRUE;
}

如果return false, 一個原因可能是與registry記錄的"Index"值不同而無法開啟。
in my case,
到 "...PLATFORM\PROJECT\FILES" -> PLATFORM.REG
然後查是否有 跟ap code 相對應的driver的 registry
如果有相對應的driver存在，檢查
"Prefix"="COM"
"Index"=dword:6
可以看到此driver是透過COM6，因此只要把sample code的 COM7 改成 COM6 就可以溝通了