I've modified the abstraction I have already made for communication with the Arduino, and restricted them to two, [serial_print] and [serial_write], which work with the corresponding Arduino functions.
[pack_comport] and [serial_println] are now deprecated and no longer in GitHub.

You can find the new abstractions here https://github.com/alexdrymonitis/Arduino_Pd

The two images below show how simple it is to use them


and the [serial_write]

Help patches and Arduino code included.