arduino to pure data on a mac


i've some trubble with some data-sending.

pure data: 0.43.1 arduino: one

i'm using an light-sensor and try to sent the data to pure data. i've selectet /dev/tty.usbmodemfd131 and the serial monitor show me some good numbers. in the mac-terminal, i get the numbers to by using the terminal with "screen blablabla" (and i kill it after looking some times at the numbers) in pure data then i get i create an objekt and i use "comport tty.usbmodemfd131 9600" in it - but there i get an error:

[comport] ** ERROR ** could not open device /dev/tty.Bluetooth-Modem: failure(16): Resource busy

[comport] opening serial port 0 failed!

but terminal doesn't write something with "lsof /dev/tty.usbmodemfd131"

i get some help in a chat for 2,5 h till now, but i'm not able to make it work. i know there are some help-files in pure data, but i don't understand the code and so on. so i need some help to get the data in pure data.

thank you; sorry for my bad english.