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COM port number assignment - and other cool technical things:
I lied. (Hey that was 5 years ago when USB was new, Windows was Win98 and I was dumber than I am now - well at least dumber about USB anyway).
Our cable (aka USB device) does not remember what COM port number it is, no,
it's remembered by the OS (Operating System) in this case Windows.
Our cable talks to Windows when it's plugged in. Windows says: "Hey, who are you?"
We say: "VID,PID,sn ..." which is Vendor ID (0711), Product ID (0243), Serial number ( unique #).
Windows takes the VID and PID to find and load a driver - and between the driver and Windows they figure out what COM port number based on the serial number. The first time it was installed Windows realized it's a new COM port and looks around for an unused number because you can't have two serial ports with the same number assigned. Often we are assigned COM 4. And if you plug in another it will be 5, etc. And the number is recorded in the regestery of that system. So because each of our units is unique in the universe and you can add 100 to one system and windows will remember the COM port number for each individual one - you can remove #37 and replace it with a new unit which will be assigned COM 101. You can force COM 101 to be 37, no problem with Device manager. Just make sure you don't plug in the old #37 at the same time the new #37 is in because it won't work like party-line time. These are very cool powerful tools, so it helps a lot to know whats going on else you can get into trouble. For instance, there are some applications where you'll always have just one plugged in at a time and you'd like them all to be COM #1 all the time in all systems. No problem. Just set each one to be COM 1 via Device Manager for every system - and when you buy a new one, just make it COM 1 and now you have total control over all your systems in the field and can interchange our units.
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