midi input from what...?
if you are using a gameport-to-midi adapter cable plugged into a computer, some of the cheap ones arn't properly opto-isolated so you might be able to do it that way, because gameports have several 5v lines. Bear in mind, though, that midi data packets only last 200ns (or something like that).
However, if you're using standalone midi equipment, as Nigel says, its no-go.
I don't know what you're trying to do, but have a quick look at:
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