I just got an UNO as a give today and was eager to play with it so I hooked it up and fired up the Arduino IDE only to find out it keyed my Ham Radio rig which uses a USB serial adapter which I had monitoring!
The UNO presented itself as /dev/ttyACM0 which is what's selected and I've successfully uploaded a simple program to test.
My ham radio uses /dev/ttyUSB0.
I've monitored /dev/ttyUSB0 using statserial and watched the IDE raise RTS on ttyUSB0 even though ttyACM0 is what's selected.
Worse, it doesn't drop RTS when I close the IDE, it just leaves it raised.
I understand that the IDE may need to "probe" the available serial ports but it should not make any permanent change to a port since something else may (and in this case IS) using it.
Thanks,
Richard