HDMI 5 port switch detecting LED with Arduino
The problem with current sensing is that you have to "divert" the current through your current sensor. It should be possible to get working but I think there's a much easier solution !
If the 5-port HDMI switch is anything like the one I have, which is this one then there will be 5 LEDs in it connected like (please excuse me for only drawing 3 LEDs, you can imagine the other 2 ;-) :







simulate this circuit &ndash; Schematic created using CircuitLab

If you connect the ground connection of the HDMI switch and also the 5 V supply (there's a connector for this supply !) then you can detect the LEDs switching on and off by monitoring the voltage on D1, D2 and D3. Such a line will be pulled to ground (0V) when the LED needs to be on.

It is possible that the circuit is implemented "upside down" so that the LED's have the ground rail common instead of supply. But also then, you can just detect the output voltages the same way.