MNet-DACS: multi-level network data acquisition and control system

This paper describes the implementation of a distributed data acquisition network based on the 80C592 microcontroller from Intel. Each station is connected in an hierarchical way to form a tree topology. The lower level network stations, designated by slaves, are dedicate to the data acquisition and the generation of control signals. The upper level, masters, are responsible for the communications control. Both networks use a CAN (controller area network) bus, for data transfer, and the global network is also connected to a PC, via a CAN. A device router, NetManager, was implemented to support total intrinsic requirements at the communication level. This type of connection allows total configuration from a personal computer, PC, which runs a software application developed for Windows(TM) environments. The tests performed at the laboratory, with transmission rates varying from 40 kbits/s to 1 Mbits/s, showed that the communications were performed without errors for cable lengths of 1100 m to 40 m, respectively. This system is now being installed in a set of environmental chambers and greenhouses located on a Portuguese university campus, where it will monitor and control air temperatures and humidities, CO/sub 2/ and ammonia concentrations and the radiation level.