Hi Maziar,

nothing of RS485, CAN, I2C can be used on only 2 wire !
You need minimal 4 wire (2 signals, ground, power).

But the 4-20mA current loop can really used with 2 wires, since powered over the same line.

And on the digital side the Dallas 1-wire-devices also, but its many more restricted in respect of noise and line length.

Some years ago TI build the Meter-Bus, which also use the same 2 wires for power and for data, but it seems canceled.


Peter