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I guess it depends on what and how much hardware input you require? I've never stress-tested the [hi] object, so I don't know what it's tolerance level is . . .

Probably best to go into USB MIDI class compliant mode, so you just come in as MIDI straight up.

I just bought a Teensy for that very reason.

(The teensy, as it turns out, has very robust usb mode implementation, so you can still reprogram it while in USB MIDI mode, unlike an Arduino, which you have to reflash the USB chip every time you want to reprogram the actual Arduino board).

+1 for the teensy, I use it both as a midi device and as a serial device with max and the speed is really impressive !

Since I had problems with the serial object (may be due to misuse on my part), I use nodejs to retrieve information from Arduino, and route it to max via udp. There are modules for Aduino through nodejs, programming the Arduino can be achieved through js script, relatively simple for beginners. Nodejs indeed allows me to send data simultaneously to a website, convenient for me. Now is that this configuration is the most efficient, I do not know, however, it meets my needs effectively