TK. 0 Posted March 12, 2012 Report Share Note: it seems that this modification is only required for MIDI devices which don't comply to the MIDI specification! Usually the MIDI IN port of a device has to work correctly when the current through the MIDI wire is at least 5 mA. 3.3V / (3 * 220 Ohm) = 5 mA Quote Link to comment
norbim1 4 Posted May 8, 2012 Report Share I think, that the opto LED opening voltage is missing form the equation....It's 1.3-1.5 V typ. In case of 6N138 at the receiver side, the 3.3V supply cannot cause any problem. But it's problematic if you use 6N136 as suggested somewhere. I've some bad experience..... Quote Link to comment
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