CANopen

CANopen is a CAN based communication protocol.

The CANopen standard is useful as it enables off-the-shelf interoperability between devices (nodes) in e.g. industrial machinery. Further, it provides standard methods for configuring devices - also after installation.

CANopen was originally designed for motion-oriented machine control systems. Today, CANopen is extensively used in motor control (stepper/servo motors) - but also a wide range of other applications, such as Robotics, Medical and Automotive.

CANopen is a “higher layer protocol” based on CAN bus. This means that CAN bus (ISO 11898) serves as the 'transport vehicle' (like a truck) for CANopen messages (like containers).

In a CANopen network, several devices need to communicate. For example, in an industrial automation setup you may have a robot arm with multiple servo motor nodes and a control interface/PC node. To facilitate communication, three models exist within CANopen - each closely linked to the CANopen protocols that we look at shortly. See below for a brief introduction:

●       Master/Slave: One node (e.g. the control interface) acts as application master or host controller. It sends/requests data from the slaves (e.g. the servo motors). This is used in e.g. diagnostics or state management. There can be 0-127 slaves in standard applications. Note that in a single CANopen network, there can be different host controllers sharing the same data link layer.

●       Client/Server: A client sends a data request to a server, which replies with the requested data. Used e.g. when an application master needs data from the OD of a slave. A read from a server is an “upload”, while a write is a “download” (the terminology takes a "server side" perspective).

●       Consumer/Producer: Here, the producer node broadcasts data to the network, which is consumed by the consumer node. The producer either sends this data on request (pull model) or without a specific request (push model).