5 ms·
> MIDI is simple enough to trigger something with a single pin going high low. MIDI is not high / low but current on / current off.
by someweirdperson 3y ago
> MIDI is simple enough to trigger something with a single pin going high low.
MIDI is not high / low but current on / current off.
- henearkr 3y agoIsn't it roughly the same, if the IO you're speaking to is pulled down through a resistor to the ground?
- cma 3y agoDoesn't MIDI require optical isolators and the only part connected to ground is the cable shielding?
- detaro 3y ago"require". But even if you add them (you should!), it's not like driving it gets any more complicated on the controller/software side, which is what notmypenguin was talking about I think
- henearkr 3y agoAnd if they are pulled down to a low reference voltage independent from the ground? (thx, I didn't knwow about required independence from the ground)
- colanderman 3y agoThe input to an optoisolator (i.e., an LED) is two pins, with no reference to ground. So either current is flowing through the opto's input, or not. Because they're not referenced to ground (or any voltage), the voltage on either pin relative to ground is irrelevant. (In this way, two connected MIDI devices can have different ideas of what signal ground is without causing issues.)
- colanderman 3y agoThe reality is "somewhere in between". It's actually specified as a voltage source with a fixed impedance [1]. Tricks like snaking the signal in series through multiple receivers don't really work; whereas tricks like sourcing +5 VDC from the connector do work. But it is correct that the current which ends up flowing through the connection is what determines the bits sent (by virtue of the receiver being an optocoupler, not an op-amps). [1] https://midi.org/specifications/midi1-specifications/midi-1-addenda/5-pin-din-electrical-specs https://midi.org/specifications/midi1-specifications/midi-1-...