It takes me something like 30 seconds from when my core boots until it is connectable via /dev/ttyACM0. Just after program start, the device pops up, but trying to get the output from there gives me:
$ cat /dev/ttyACM0
cat: /dev/ttyACM0: Device or resource busy
Is this usual, or is something derped up on my admittedly hackedy Linux Mint Laptop?