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CANopen: a higher-layer CAN communication protocol

Written by
The MurCal Blogster
Published on
December 30, 2022 at 1:09:40 PM PST December 30, 2022 at 1:09:40 PM PSTth, December 30, 2022 at 1:09:40 PM PST

In many real-time industrial applications such as robotics (automated robots, conveyor belts and other industrial machinery), medical (X-ray generators, syringes, hospital beds and dialysis equipment), transportation & automotives (agriculture, railways, trailers, heavy duty, marine, etc.), and aerospace, CANopen offers a standardized and highly configurable solution. 

A bit of History:

Robert Bosch introduced the CAN (Controller Area Network) serial bus system at the SAE congress in Detroit in 1986. The protocol supports short messages (up to 8 bytes), multimaster access (collisions are resolved based on priority), and offers high reliability (15-bit CRC for every message).

By 1987 Intel delivered the first CAN chip, followed by Philips Semiconductors.

There are about 20 chip manufacturers today who make devices with CAN interfaces, and almost every new vehicle in Europe is equipped with a CAN network. One of the most widely used bus protocols, CAN is also used in trains, ships, and industrial controls.

In 1993, ASPIC, a European consortium led by Bosch, developed a prototype of CANopen, an internal networking profile based on CAL. CiA released the completely revised CANopen communication profile in 1995. In addition to defining device, interface, and application profiles, the CANopen profile family also defines a framework for programmable systems. It is for this reason that whole industry segments (e.g. printing machines, maritime applications, medical systems) chose CANopen in the late 1990s.

What is it

It is a low-level protocol for industrial automation applications, similar to J1939. CANopen uses peer messaging to connect automation devices. Based on the CAN physical communications standard, CANopen defines an application layer protocol that organizes the task of configuring, accessing, and messaging between various kinds of automation devices.

Various applications use it today, including medical equipment, off-road vehicles, maritime electronics, railway applications, and building automation.

CANopen is a protocol based on the CAN bus that belongs to the "higher layer".

The CAN bus (ISO 11898) serves as a vehicle for CANopen communication. (see image below)

In other words, CANopen handles everything above CAN, including choosing what physical path the data will follow, maintaining a stable connection, ensuring data is usable, and providing simple integration with your application.

A CANopen device includes three parts:

* Communication via the CAN network is handled by the CANopen protocol stack

* Application software that provides internal control functions and interfaces with process hardware

* Both the protocol and application software are interfaced through the CANopen Object Dictionary. All communication and application parameters are stored here as well as references (indices) to all types of data used.





CANopen is on one hand standardized, but on the other hand, it is still open to a nearly unlimited field of applications.


In CANopen, designers can implement desired network behavior into devices using several communication objects. With these communication objects, device designers can offer devices that can communicate process data, indicate device-internal error conditions or influence and control the network behavior. Due to CANopen's definition of the internal device structure, system designers are able to access CANopen devices and modify their behavior.


With CANopen, the developer does not have to worry about CAN hardware-specific details such as bit timing and acceptance filtering. For time-critical processes, configuration, and network management data, it provides standardized communication objects (COB).


CAN-frames are identified by 11-bits which are called communication object identifiers or CANopen COB-IDs. When two frames collide, the frame with the smallest id is transmitted first.


In comparison to traditional serial servo drives and motor controllers, CANopen servo drives and motor controllers offer many advantages. With CIA standard object dictionaries, applications can be developed faster and slave devices and master controllers can communicate more efficiently.


Reusing application software is very important for system designers. Devices must be interoperable and interchangeable, in addition to being compatible with communication. CANopen is a standardized interface format for devices, interfaces, and applications, enabling device manufacturers to create CANopen devices that plug and play. Manufacturer-specific functionality can be implemented using CANopen.



Since CANopen is the preferred interface in Europe (in the US the J939 is more popular) it comes as no surprise that some of our most popular CANopen products are from European Manufacturers. 


For example, we carry Beckoff Automation Terminals, CRE Technology’s Compact Generation Controls & Blink Marine’s Power Pro-Series Keypads which all have a  CANopen interface. 


It is important to note, however, that various products on our website have a CANopen interface, such as the PV450 from Enovation Controls.


Contact us for help in determining which module will work best for your machinery.

Phone: 661-272-4700

Email: sales@MurCal.Com

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