Hello,
i want build a midi input circuit to arduino.
I found two examples:
http://www.instructables.com/id/Send-and-Receive-MIDI-with-Arduino/3/
and the second one:
the first one is easier and directly. And it would be cheaper for me.
The second example has an optocoppler and a diode. Diode proctects incorrectly wired Midi cable. But whats the reason for optocoupler? So it is dangerous using first example without any components?
The first one also uses an optocoupler, see section 9 on Receiving MIDI messages.
From Wikipedia:
Opto-isolators keep MIDI devices electrically separated from their connectors, which prevents the occurrence of ground loops and protects equipment from voltage spikes. There is no error detection capability in MIDI, so the maximum cable length is set at 15 meters (50 feet) in order to limit interference.
The reason for using optocouplers in midi (it is even specified that way) is to avoid ground loops.
okay thank you all very much