[PD] Arduiano (Micro or Nano) as MIDI interface?

[Ingo]

Hi there!

I'd like to use an Arduino Micro (or Nano) as a MIDI interface connecting
the MIDI ports to the digital pins "0" and "1" (TX/RX) and receiving the
MIDI data via USB in Pd.
It does not matter in which format it comes into Pd (i.e. it doesn't have to
show up as a MIDI port - like MIDI over USB).

1) Does anybody know if there is an existing arduino software for this?

2) Does anybody know if there are limitations on some or even all arduinos
using the serial (digatal 0/1) ports and USB port at the same time?

(BTW, I'm already aware of the electronic parts that are needed for the MIDI
In/Out.)

Thanks in advance!

Ingo