Development of a Remote Serial Cable over GSM

Resumo

Diverse monitoring and control applications require that a host computer communicates with one or several remote units (sensors, actuators, …). Usual off-the shelf communication links require that both host computer and remote units adapt themselves to data protocols or physical properties of the devices that implement the link. Since almost all remote devices have a built-in microprocessor, which usually has one or more UART transceiver, a communication link was designed to workover this interface with the objective of minimizing the hardware and firmware changes required on both ends of the link. This article presents the design and implementation details of this communication link, which was denominated Remote Serial Cable – RSC. The RSC is a hardware interface that allows bidirectional communication between remote equipment and host computer, being that communication channel seen by both ends as a transparent RS232 connection, as if they were connected directly through a standard serial cable. It uses the GSM network to communicate between RSC Units, transporting the data through SMS, Circuit Switched Data (CSD), or GPRS.