Does anybody know how much is the voltage difference when logic 0 appears between 4th and 5th pin of an MIDI output conector? I have Agilent 4N25 optocoupler and i don’t know how to set it rigth for midi transmition.
So far I tested optocoupler working as a switch for an simple LED running in the other side of optocoupler. When I want to connect an RX (pin 0) of Arduino Duemilanove to the circuit, the input doesn’t read anything.
In the manual it says that typical Vf 1.2 V must be on 1st , 2nd pin for 10mA current flow through. But I don’t know how to set it to 1.2 V because I don’t know the voltage drop between 4th and 5th pin.
I decided that 220 Ohm would be just fine, also everyone on the web use it so I suppose it would make enough current to control a diode inside optocoupler, but on the other side nothing happens still. When I’ running a LED for indicator it says that the current flows right.
Why my arduino reads nothing. Is there some mistake in the circuit or it’s a only problem with my arduino serial input, because without optocoupler RX input works just fine. So?
Can someone help me to find mistake in this situation please!