Automatic addressing process for devices on a serial bus

An automatic addressing process for devices on a serial bus is disclosed. In one aspect, a controller is communicatively coupled to multiple power supply units (PSUs) over a serial bus. At installation (and may be at start up or reset), the controller sends a signal through the serial bus to a first PSU, which adopts a first address based on a voltage level of the signal and increases the voltage level before passing the signal to a second PSU. The second PSU adopts an address based on the increased voltage level, increments the voltage level of the signal and passes the signal down the bus. Adopted addresses are written to memory and stored in such a manner that power loss will not erase the address. This stepped voltage signal allows multiple identical PSUs to be addressed without reliance on manually-changed dip switches, separate address negotiation software, or the like.