I found this schematic and after checking with official documentation it seems to be fine
However, since my board is 3.3V I have to make few alterations. My questions are:
On TX side:
- I replace the R from 3V to 5din to 33 Ohm?
- I replace the R from TX to 5din to 10 Ohm?
On RX side:
- Do I change R between 5 din and a diode? I'm pretty sure I don't but want confirmation
- 1N914 isn't terribly required, right? Can be 4001, 4008, 4148?
- 4n35 doesn't seem what most people use, can get away with 6n138, can't I? Or is H11L1 absolutely necessary?
- I'm pretty sure I have to change the resistor that pulls RX to 5V (3.3 volt in my case), MIDI specs say "Value of RD depends on optoisolator and V RX" and then provides no further explanation - how do I calculate that for both 6n138 and H11L1? There are schematics I found that opt for 470 Ohm, but I don't follow the reasoning behind that
- Why should I pull up RX pin in the first place? Isn't it pulled up after I declare begin(BAUD)?
Thank you for your time, I really appreciate that