US Patent 7650449 Communication system for devices with UART interfaces

A UART interface communication circuit includes a plurality of communication devices, and each includes a UART interface, a selecting apparatus, a CPU, and a multiplexer (MUX). The communication devices connect with each other via the UART interfaces thereof. The selecting apparatus is connected to the CPU for defining one of the communication devices as a master communication device and the rest as slave communication devices. The MUX is connected between the UART interface and the CPU. When the master communication device transmits data carrying an ID to the slave communication devices, a slave communication device corresponding to the ID receives and processes the data, and transmits return data to the master communication device, and then the MUX receives the return data from the slave communication device and passes it to the CPU of the master communication device for processing.