I need my puredata comport object to open the same port of the arduino each time the patch is started

How can I make sure it will happen?

I have try to use the message [devicename] in order to set the device name ( I guess the name will not change every time pi or pd are restarting) but I'm getting an error:

I did the following:
same method to choose the audio interface, just doing it for ports.

The only think that must be constant is the names of the ports on the Raspberry pi (in thatexample I'm using windows pc)

This method should work?
the name of the ports are always the same on raspberry pi?

Any other method for setting the port?
Do I also need to change the code in the arduino? to prompt something to the serial?

Port_choose.zip

And in term of orders of banging:
First I'm choose the audio interface (area marked in red)
then if match was detect it will set the audio settings and start the dsp.
same bang will also bang the system to choose the port.
Does it make sense? or i can set both audiosettings and port for arduino at the same time (sending loadbang to both system (audio device chooser and port chooser at the same time)

The example above is using a windows computer but the acctual patch will be on Raspberry pi

I suggest you first try it on the Pi, and then post potential problems. I'm pretty sure that if your Pi setup doesn't change, meaning that the Arduino will always be plugged in the Pi, you won't have a problem. Right now you're likely creating an issue where there shouldn't be any, by trying out something on your Windows computer, assuming your Pi setup will behave the same way.

you were right, it seems that each time pi is rebooting it still recognize arduino at the same port (1) .
I also noticed that is it not matter if I plug the arduino to port 1 of the USB2 or port 2 of the USB2 it will still have thae same index(1); does it make sense?

So in any case - the system I share for setting the port by name is working just fine so I might just leave it or is better just [loadbang] --> [open 1] ?

If you don't change the hardware configuration and leave the Arduino plugged in (especially if you don't have any other serial devices plugged in), the I think it's the same whether you open by name or number.