Is it possible to make a pass through ?

[cgiles]

I wonder if it is possible to make a pass through, by using the second output, and calling it via the callback of the input ?

Or it would be too slow ?

[claudeheintz]

There's no reason that this would not work. But, to be useful, you'd probably be doing something between the input and output. As long as that didn't hold up the serial interrupts, it would be fine. Things that hold up serial interrupts (like some serial LED hardware/libraries) require you to have a strategy for the input that accounts for potentially missed input bytes.