Practical evaluation of messages latencies in CAN
Javier Gámiz, Josep Samitier, Josep M. Fuertes, O. Rubies · 2004
In the area of process automation it is increasingly frequent to find control loops that close through communication networks, giving as a result what we know as distributed control systems. The CAN fieldbus (controller area network) is a solid industrial network, with a high baud rate and a capacity for error detection that makes it ideal for aggressive electromagnetic environments. The special idiosyncrasy of CAN, with protocols based on message priority, makes it especially interesting for the implementation of real-time control systems. Here, a CAN node realization is presented. This is useful for industrial and/or educational applications because it allows the study and analysis of the delays suffered by the messages. It is based on a model for the planning of deadline monotonic (DM) type tasks in a global system controlled by CANalyzer. The calculation of the worstcase delay has been carried out by means of the jCAN1 software tool, previously validated on a specific theoretical example. Finally, the results are evaluated and verified, and discussed with reference to the practical results obtained in a multi-node system constituted by a group of identical nodes to the one designed here.