I am using 6n137 opto-coupler to take engine tachometer 12v signal from ECU, then send it to arduino nano esp32 that in return it drives rev RGB LEDs. I found in the optocoupler data sheet that the minimum input voltage is 4.5V at Vcc. Is it ok if i supply Vcc with 5V and pull up Vo to 3.3V from the arduino, to get 3.3V pulse output? as shown in below figure.
Your topic does not indicate a problem with IDE 2.x and therefore has been moved to a more suitable location on the forum.
From the datasheet it seems open drain like.
So your idea might work...
Better measure output voltage before connection to GPIO...
That circuit works if you have common GND between tach and esp but then you really don't take advantage of optoisolation. Connect GND pin to esp GND.
The gnd on the righthand side should be connected to the arduino!
The only connections to the Arduino are the optocoupler pins 5, 6, 7, and 8. Pins 2 and 3 connect only to the tach signal. The tach signal should not be connected directly to the Arduino if you want isolation, @build_1971. The output side of the optocoupler will drive the Arduino input.
Are you sure your ECU can supply enough current to activate the 6N137. If it can't, you could damage the ECU.