I have an Odroid which I use either with an SD card or an eMMC module, both with the same OS (Debian Jessie for Odroid). In the SD card I've got Pd-0.45-5 and in the eMMC module I've got Pd-0.46-0 installed.

With the SD card I can open the port /dev/ttyACM0 (I've got a Teensy 3.1 plugged in via USB) but with the eMMC module I get this error:
"[comport] ** ERROR ** could not open device /dev/ttyACM0:
 failure(13): Permission denied"

Any idea why is that? And how can it be solved?

I've checked the /dev/ directory and the port exists in both the SD and the eMMC.