A method of communicating on a single serial line between two devices is disclosed. The method includes combining a data stream and a clock to form a three-voltage level stream such that the third voltage level records the transitions of the clock while the serial data is either high or low. Either the first or the second device can send a combined stream on the line. The method further includes, in some embodiments, the second device driving the same voltage levels as those transmitted by the first device and the first device sensing current on the single serial line to determine that the second device has received data from the first device.