I cannot get opto-coupler H11L1 to work as MIDI Input
Remove the opto-isolator from the breadboard. Replace it with an LED. That should blink when you transmit from the MIDI source device.
If that's OK then put the opto-isolator back in. Put the LED in series with the pull-up resistor. Repeat the test and you should see the LED blink.








simulate this circuit &ndash; Schematic created using CircuitLab