Serial Ports, CreateFile and SetCommState

Question

I'm using Windows API's CreateFile and SetCommState functions to open a number of serial ports to read and write from, selecting ports using this notation:

\\?\COM1

I've been logging performance closely, and for some odd reason the CreateFile call takes about as much time as the SetCommState calls do (about 4.1 seconds).

I find this very odd and makes me suspect that both CreateFile and SetCommState perform a set of similar tasks with the windows subsystem that handles serial port communication.

Could there be a way to speed up one of both calls, or eliminate one, for example calling CreateFile in such a way it already uses the DCB I've got prepared to call SetCommState with?

Answer 1

The documentation you posted suggests calling GetCommState to initialize the DCB structure. I wonder if the delay is because you're setting something you don't care about? For what it's worth, I've noticed much bigger delays opening Bluetooth virtual COM ports than regular or USB ports.