[sdiy] Possible MIDI interface powered by MIDI driving device...

[Olivier Gillet]

> Steve T's comment about 5V not being a reliable supply suggests to me that for things like this (let's call it "creative rule-bending"?!) we should use uPs that can operate from 5V down to 3V or so. There are such things, so this shouldn't be too difficult to organise.

The value of the resistors on the OUT side depend on the supply
voltage. If the MCU is powered by 3.3V, they should be much lower than
220 ohm (about 50 ohm) - otherwise you won't be sending enough current
in the loop!