A system for automatically addressing serially connected slave devices includes a master device and multiple slave devices each including a serial communication transceiver, an address input port, an address output port, and a controller. The system also includes a serial communication wiring bus connected between the serial communication transceivers of the master and slave devices, and at least one digital address line connected between the address input ports and the address output ports. Each controller is configured to receive a PWM or PFM signal from a previous one of the multiple slave devices, determine an address for the slave device including the controller according to the received PWM or PFM signal, and transmit a PWM or PFM signal indicative of the determined address to a subsequent one of the multiple slave devices.