Determining the Physical Sequence of Sensors on a Serial Bus With Minimal Wiring

This report demonstrates a three-wire system for determining the physical sequence of addressable devices on a serial bus, enabling automated spatial mapping of sensors along a network. Small inductors between each chip are incorporated into an oscillator circuit, producing a different resonant frequency for each chip during the sequence detect function. Frequency-counting-based sequence detection is compatible with small microcontrollers such as those used in wireless environmental sensor networks. The sequence detection hardware does not interfere with normal use of the same three wires to supply power, data, and ground connections to the wired sensor network in this application.