Hi all, I just started playing with Teensy and am much more used to editing, compiling and running code from a text-editor so I'm not a massive fan of the IDE. Hence I wanted to communicate with my Teensy via /dev/ttyACM0. To do this I found it useful to make a small modification to the udev rule, changing the KERNEL== line by adding to the end of it:

, RUN+="/bin/stty -F /dev/ttyACM%n -echo"
(so mine now reads
KERNEL=="ttyACM*", ATTRS{idVendor}=="16c0", ATTRS{idProduct}=="04[789B]?", MODE:="0666", RUN+="/bin/stty -F /dev/ttyACM%n -echo"

This changes the device so that it doesn't echo output back to the input, which tends to break everything if you are doing bi-directional serial communication. I assume the IDE does something like this automatically, but if you aren't running it, it doesn't work.

Hopefully this helps someone else!

P.S. I don't know if this will break something else... YMMV etc.