Can't open COM1 from application launched at startup
- by n0rd
I'm using WinLIRC with IR receiver connected to serial port COM1 on Windows 7 x64. WinLIRC is added to Startup folder (Start-All applications-Startup) so it starts every time I log in. Very often (but not all the time) I see initialization error messages from WinLIRC, which continue for some time (couple of minutes) if I retry initialization, and after some retries it initializes correctly and works fine. If I remove it from Startup and start manually at any other moment it starts without errors.
I've downloaded WinLIRC sources and added MessageBox calls here and there so I can see what happens during initialization and found out that CreateFile call fails:
if((hPort=CreateFile(
settings.port,GENERIC_READ | GENERIC_WRITE,
0,0,OPEN_EXISTING,FILE_FLAG_OVERLAPPED,0))==INVALID_HANDLE_VALUE)
{
char buffer[256];
sprintf_s(buffer, "CreateFile(%s) failed with %d", settings.port, GetLastError());
MessageBox(NULL, buffer, "debug", MB_OK);
hPort=NULL;
return false;
}
I see message box saying "CreateFile(COM1) failed with 5", and 5 is an error code for "Access denied" error according to this link.
So the question is why opening COM-port can fail with such error right after booting Windows and proceed normally few seconds or minutes later?
