New to Arduino (first week) and first post of the forum. So far just been playing around with buttons, LEDs and made a simple game using the 9x9 matrix and joystick supplied with the kit.
I purchased from my local electronics store an "Arduino starter kit" and what I thought was a stand alone Arduino Uno R3.
The board in the starter kit has no labeling on it other than "UNO" printed and the other board is a Keystudio UNO. I'm not sure if either of these are actually genuine Arduino but they both appear to work OK.
Anyway I'm trying to understand what a "port" actually is. When I plug the blue board in I need to select "COM3" but when I plug the Keystudio in I need to select "COM4". I had thought that COM3 and COM4 etc was the physical USB hardware plug but obviously not. Is there some reference material I can read up on to educate myself on this?
USB is "Universal Serial Bus." When you plug something in to a USB port, a bunch of communication between the device tells the computer what sort of device it is, and perhaps connects it to the correct driver.
In the case of Arduino Uno (including clones), there is a USB chip that tells the computer "I am a COM port!" The computer then creates a COMx port unique to that USB device - if you're lucky the same device will always appear as the same COMn (ie your blue board will always be COM3, and the keystudio COM4), but that's not really guaranteed (you are guaranteed that if you plug in multiple boards at one time, they'll all get unique numbers.)
(I think COM1 and COM2 are sort-of reserved for actual non-USB UARTs that might or might not be implemented on your motherboard. I don't think I've ever seen an Arduino show up as anything lower than COM3.)
(plug in other devices, and the show up otherwise. A thumb drive says "I'm a disk", a mouse says "I'm a mouse", and so on. That's what makes it "Universal.")