CANopen implementation using BCP protocols over TIA-485 in networked embedded systems

Abstract

CAN (Controller Area Network) and TIA-485 are two of the most used standards in fieldbus systems. While CAN ISO IS-11898 includes complete data link layer specifications on top of its physical layer, TIA-485 only addresses the physical layer of the 7-layer OSI model. Other communication parameters like speed, format, and data transmission protocol are not specified by RS-485 in order to provide interoperability of similar devices from different manufacturers. After a brief introduction and comparison of the two communication protocols, the paper investigates to what extent the CANopen specification - an application level protocol developed primarily for CAN networks - should be used in TIA-485-based fieldbus networks in order to provide the user an application programming interface (API) independent of the physical layer. Selected and customized CANopen services have been implemented and tested on a network of microcontroller-based stations equipped with CAN ISO 11898 and TIA-485 communication interfaces.