CANopen is a communication protocol and device profile features for embedded systems used in automation.
The CANopen standard consists of an application scheme defined by an addressing scheme, several small communication protocols, and a device profile.
Communication protocols support network management, device monitoring, and communication between devices, including a simple transport layer for message segmentation.
The downlink protocol that implements data connectivity and physical layers is usually the Controller Area Network. (CAN), but other communication
devices using CANopen can also implement the device profile (such as Ethernet Powerlink, EtherCAT). The basic CANopen device and communication profiles are provided in the CiA 301 specification published by CAN in Automation (CiA).
Profiles for more specific devices are built on top of this basic profile and are specified in many standards published by CAN in Automation, such as the CiA 406 for encoders.
Each CANopen device must implement certain standard features in the control software.
• A communication unit implements messaging protocols with other nodes in the network.
• Starting and resetting the device is controlled by a device that manages the network.
Start, Pre-Operational, Operational and Stopped states. Transitions between states are made by giving the device network management (NMT) communication object.
• The object dictionary is a set of variables with a 16-bit index. In addition, each variable may have an 8-bit subdirectory.
The variables can be used to configure the device and reflect the environment, ie it contains measurement data.
The application part of the device performs the desired function of the device after the network management device is put into operation.
The application is configured by variables in the object dictionary, and the data is sent and received through the communication layer.
An Electronic Data Sheet (EDS) is a file format defined in CiA 306 that defines the communication behavior and object dictionary entries of a device.
This enables tools such as service tools, configuration tools, development tools, and others to use the devices correctly.
These EDS files are required to pass the CiA CANopen compliance test.