Actually, I’ve tested from version 16 back to version 05 (the earliest that will run on an Intel Macintosh with Mac OS X 10.5.7!)
Here’s the sequence of actions -
- Go to the ‘Tools > Serial Port’ menu. One of the ports is checked. Let’s assume that it isn’t the port that you want to use, so you select a different port. The menu closes.
- Now you realize that you picked the wrong port, so you re-open ‘Tools > Serial Port’, and, lo and behold, you have two ports selected! :-?
- You can continue doing this; ports are never de-selected.
The only way to determine which port is really being used is to quite the Arduino IDE and relaunch.
(I found this bug while demonstrating the IDE to a group of students - it was moderately embarassing when I couldn’t determine if the serial connection was working, since I couldn’t determine which (of all the ports selected) was being used - or it the IDE was talking to all of them!)