Can one power a I2C slave with a separate power supply from the mcu power supply?

I know one can have multiple masters do they all need to use the same power supply?

I tried using a battery for the slave but it didn't work so I thought I'd better ask.

In trying to think through the logic I can see where separate power supplies might not work but it does seem practical if you are using remote slaves.

If you have to use a common power supply that makes I2C a four wire not a two wire system.

I suppose you would call the "bus" two wire.

Thanks for the clarification,

Ralph

You will have to have a common ground between the them. So, 3 wires, 2 for I2C and 1 for GND.

Oh, so the wired common ground (3 wires) would work. That makes sense.

Now I wonder if "Earth Ground" would work?

Years and years ago I used to setup field telephones while in the Army using "phantom" wiring.

We could get a extra circuit using earth ground.

I do not see earth ground mentioned in modern day electronics.

I know I could run three wires or two pair wiring as easy as two wires but it's so interesting, and I am so cheap.

Thanks Paul,

Ralph