Thanks for posting this! I really appreciate having an approach to use print instead of write. It makes it much cleaner to use a simple data packet and parse it in Pd.

I created a bi-directional example that can be expanded to easily support more bytes which can be downloaded here:
https://github.com/Jiffer/mmArduinoPd

It uses a single character to indicate the beginning "A" and end "a" of a packet, which opens and closes a gate without using [bytes2any].