Two-wire communication apparatus and method

Abstract

A method and apparatus for operating and actuating remote devices using a single pair of wires together with communication and networking protocols necessary for operational control of the remote devices and data gathering activities from the remote devices. The invention leverages the use of existing wiring and is particularly useful in heating and air conditioning systems, sprinkler control systems, security systems, lighting control systems, industrial automation control systems and similar environments.

1 . A method for discovering remote units on a two-wire bus having a master unit and a plurality of remotes units, each remote unit having the ability to sink the two-wire bus to a low voltage state, each remote unit having the ability to test when the two-wire bus is in the low voltage state, each remote unit having the ability to transmit messages on the two-wire bus when the two-wire bus is in the low-voltage state, comprising the steps of:
 assigning a unique identifier to each remote unit,   the master unit issuing a discovery request on the two wire bus,   each remote unit:,
 receives the discovery request, 
 tests the two-wire bus for the low voltage state, 
 if the two-wire bus is already in the low voltage state, the remote unit delays a pseudo random amount and retests the two-wire bus until it detects that the two-wire bus is no longer in the low voltage state, 
 otherwise, sinks the two-wire bus to the low voltage state and transmits a response message to the master unit, the message having the unique identifier, 
   wherein each remote unit transmits its unique identifier to the master unit.