Techniques for communicating multi-level signals

A method, comprising:

• receiving, at a first device from a second device, a first signal at a first symbol level of a modulation scheme comprising three or more symbol levels, the first symbol level corresponding to a first multi-bit value;
• receiving, at the first device from the second device, a second signal at a second symbol level of the modulation scheme, the second symbol level indicating a second multi-bit value that corresponds to a third symbol level of the modulation scheme based at least in part on receiving the first signal at the first symbol level;
• and
• decoding, at the first device, the second signal to determine the second multi-bit value based at least in part on receiving the first signal at the first symbol level and the second signal at the second symbol level, the second symbol level being between the first symbol level and the third symbol level.

An apparatus, comprising:

• a transmission line of a bus;
• a set of receivers coupled with the transmission line, each receiver of the set of receivers configured to compare a first voltage level of the transmission line with a reference voltage level associated with the receiver;
• and
• a decoder coupled with the set of receivers and configured to determine a first symbol level of a modulation scheme indicated by the first voltage level based at least in part on a second voltage level of the transmission line corresponding to a second symbol level.