Moxa IA261-I-T-CE User Manual download pdf (Page 37)

IA261/262 WinCE User’s Manual CANopen Library

CANopen Introduction

CANopen is a field bus protocol based on the Controller Area Network (CAN). As the name

implies, it is a open network standard accepted throughout the world. While created as a field bus

protocol for industrial automation, CANopen finds use in a wide range of other non-industrial

applications. There are so many possibilities, in fact, that it is possible to write volumes on

specialized uses of the protocol. Rather than being specific to one narrow application or even one

field, we present here a more generalized approach: a generic communication stack based on

CANopen that can be tailored to the user’s needs. This article focuses only on what is covered in

the CAN in Automation (CiA) standard DS-301. In fact, most of the discussion is limited to the

predefined areas of the specification, with emphasis on understanding how the code provided with

this application note functions and how users might develop an application on the CANopen

Stack.

CANopen defines protocols for the following tasks:

• Configuring a CAN network.

• Transmitting data to a specific node or in broadcast.

• Administrate the network. For example control the state of the slave node.

The documentation can be found on the CAN automation website:

http://www.can-cia.de/canopen

The most important document about CANopen is the normative CiA Draft Standard 301, version

4.02. You can now download at no cost from the CAN automation website.

Our CANopen Stack provides the lower layers of the protocol. Some of the features of this design

include:

• Conform to DS301. V.4.02

• Master and Slave functionality

• Programmable transfer-rate 10K, 20K, 50K, 125K, 250K, 500K, 800K,1000K

• Sending SYNC

• 1 SDO server per node

• Unlimited SDO clients

• SDO transmission modes: normal, expedited, download, and upload

• Unlimited PDO receives

• Unlimited PDO transmits

• Object Data type: 8, 16, 32 bits values, and fixed length strings

• Slave state full implemented

• NMT to change slave’s state

• PDO transmission mode: on request, every reception of 0 to n SYNC, on event.

• NMT Heartbeat: A node can be either heartbeat producer or receiver.

• NMT NodeGuard: Not fully implemented.

The protocol is designed in three levels, as shown in Figure 1. The lowest level is the CANbus

driver providing hardware abstracted CAN support. The communications management level is the

primary interface between the driver and the individual endpoint handling. Besides the application,

there is also the dictionary. In essence, it resides outside of the communication object, and is

directly connected to the SDO endpoint.

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