Yes, something similar to the Dallas 1-wire. I am a hobbyist; I used the following scheme a few ago with MSP430F2xx. It works, but is probably very unprofessional. At the MSP end of the one-wire, I have a diode, capacitors, and a 3V regulator as the power supply for the MSP. The MSP RXD is connected to the wire through a resistor of a few k-Ohm so that it can tolerate +5V on the wire. The MSP TXD is connected to that wire through an open-collector driver. The MSP will use its TXD to drive that wire low only when it has permission to do so. At the host end of the on-wire, the 5V RXD is connected to the wire directly. The TXD is connected to the wire through a 5V three-state driver. And there is also a weak 5V pull-up. The host will actively drive the wire to 5V when it is transmitting a "one", a "stop", or "idling". It will actively drive the wire to 0V when it is transmitting a "zero" or a "start". However, when it is expecting the MSP to reply, it will go to high impedance state and rely on the weak pull-up on the wire. Notice that if the MSP misunderstood the host, it is possible that it drives the wire low while the host is driving it high. The hardware design must accommodate such mishaps without physical damage.
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