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Jan 7, 2014 at 8:23 comment added HenningNT Sorry for the late reply! No, you do not need a series resistor on the inputs. But remember, always check the datasheet for any device you use, it usually covers the typical usage scenarios.
Jan 2, 2014 at 17:59 vote accept dodo
Jan 2, 2014 at 17:59 comment added dodo I agree. Now I'm planning to use 74xx244 to buffer multiple input lines. I have one last question, would I need to connect series resistors to its inputs to limit current or do these 74xx devices already do it by themselves?
Jan 2, 2014 at 17:42 comment added The Photon I think this is the best solution, but if I went this way I would probably also switch to an optocoupler with totem-pole outputs instead of 6N137. FOD0721 seems to have similar speed specs and would eliminate external pull-up components.
Jan 2, 2014 at 12:32 history answered HenningNT CC BY-SA 3.0