Communication protocol design of intelligent building monitoring system based on CAN bus

Modern intelligent building monitoring system widely uses field bus technology. There are currently more than 40 types of fieldbus, but there are two main types suitable for intelligent buildings and popularized in China: CAN (Control Area Network) bus and Lonworks bus. CAN bus technology has great application potential due to its high reliability, simple structure, long transmission distance and low cost.

Control LAN is the most mature and promising microprocessor local area network in the field bus technology. The protocol adopts a bus-type topology structure. By studying the CAN2.0B protocol specification, a communication protocol that complies with the intelligent building monitoring system is formulated, and the design of the communication node software is carried out.

1 Intelligent building network topology based on CAN bus

The topology of the intelligent building monitoring system of CAN bus is shown in Figure 1. The system consists of three parts: the host computer, CAN communication node and various field intelligent equipment. The number of communication nodes can be increased or decreased according to the scale of the building. The CAN bus is used as a communication network to connect each node into a distributed intelligent monitoring system.

(1) Upper computer: It is composed of computer and monitoring software. It is the center of the entire system for the management and control of the entire intelligent building monitoring system.

(2) CAN communication node: each communication node has the same function, mainly to send the real-time data collected by the field device to the CAN bus, and receive the control information sent by the CAN bus. The hardware of CAN communication node is composed of microprocessor, CAN controller SJAl000, CAN transceiver PCA82C250.

(3) On-site intelligent equipment: composed of microprocessor and on-site functional device. Complete functions such as detection, alarm, control and display. The on-site equipment of the intelligent building monitoring system consists of lighting, air conditioning, elevators, safety monitoring, fire monitoring, water supply and drainage, and power distribution.