Quote Originally Posted by mister_e View Post
LMAO nah i don't have as this much of COM port. I only have 13. But you know, some USB-Serial (if not all) default value will be higher than COM15 - 16... which is the MSComm limit. Sure there's a way to do it with old VB version (5-6). Maybe one day i'll do a deeper API/DLL search.
The problem with USB-Serial adapters is the way that windows works.

USB is not the easy "Plug'n'play" solution that it should be. If you plug a Prolific USB-Serial adapter into a PC it is detected and assigned the next unused COM number. so lets say it gets assigned COM3

All good so far..... except next time you decide to use it you plug it into a different USB post on your PC, now Windows sees it and depite it being the SAME physical adapter it installs it again, this time as COM4

All it recognises is the Vendor ID and Product ID so ANY Prolific USB-Serial adapter plugged into your first USB port will be COM3 and likewise the secind USB port would be COM4.

If however you plugged an FTDI USB-Serial adapter into your first USB port, it gets installed as COM5 because it is a different Vendor and Product.

Worst of all, you cant uninstall an adapter unless it is actually plugged in because it doesnt exist in Device Mangler.

I was working with a piece of kit a couple of years ago that HAD to use a USB Serial Adapter and the software HAD to run on COM3. Plugged an adapter in and it got assigned COM4 because a different brand had previously been used.

I did however discover that if you change the adapter you want to be COM3 to COM3, the "other" non existant comport then gets assigned a differnt com number.

Trying to remember which adapter you used and on which USB port is a real headache !!!