Reading Arduino from Pure Data

Hi I'm new to interfacing Arduino with PD and I'm hoping someone can point me in the right direction. What I need to do is detect a hit from a Piezo sensor and send the data to PD. At the moment I've the Piezo set up to output a value when hit. I need to interface this with Pd so that a sound can be outputted when the sensor is hit.

Is it the Arduino_for_Pd_Input that sends the data to Pd? Does it need to be altered in any way?

When i click the Open message box in Arduino2PD.pd I get error - 'Write error, maybe TX-OVERRUNS on serial line'. When i turn off start and click Open i get '** ERROR ** could not open device /dev/ttyS1: failure(2): No such file or directory'

Any advice as to how I can fix this error?

I've tried both ports on my MacBook.