Optocoupler?

[SpufuZ]

Hello.
Im new to microcontrollers and DSP...

I would like to know what the optocoupler after a MIDI input in a circuit does exactly.
Is it just dividing two circuits?

//dave

[Peter Snowberg]

The optocouplers in MIDI keep the ground in each device separated from the ground in the next one, preventing ground loops which can cause problems from hum to blowing chips.

MIDI is what's known as a current loop interface where as things like RS232 are voltage level interfaces. The difference between them is that 0 and 1 on an RS232 interface are signaled by the polarity of the voltage present, in MIDI it's whether or not current is flowing through the LED side of the optocoupler. It's a more industrial strength style of interface but the speed is limited by the speed of the optocouplers.

[bioroids]

Thanks Peter, I didn't knew that!

Miguel