CANopen to Profinet Gateway: Structure, Configuration & Applications
A CANopen to Profinet gateway acts as a protocol converter, enabling seamless communication between CANopen field devices and Profinet industrial Ethernet networks. This article breaks down its internal structure, communication mechanisms, and configuration steps.
Understanding the CANopen to Profinet Gateway
In modern industrial automation, integrating legacy fieldbus systems with high-speed Ethernet-based protocols is a common challenge. The CANopen to Profinet gateway solves this by bridging the robust CANopen protocol—widely used in embedded systems and drives—with Profinet, a leading industrial Ethernet standard. This gateway is essentially a smart node that translates data objects, timing, and network management between the two worlds without requiring complex user programming.
CANopen itself is built on the Controller Area Network (CAN) physical layer, adding a higher-layer protocol with communication and device profiles. It is prevalent in applications like servo drives, encoders, I/O modules, and sensors. Profinet, on the other hand, offers real-time data exchange, diagnostics, and IT integration. The gateway makes it possible to connect CANopen devices to a Profinet controller (such as a PLC) as if they were native Profinet nodes.
Internal Architecture of the Gateway
The gateway’s architecture can be divided into two main sides: the CANopen interface and the Profinet interface, with a processing core that handles data mapping and protocol conversion.
CANopen Communication Objects
On the CANopen side, the gateway operates as a CANopen master (or sometimes a slave, depending on configuration). It manages the CANopen network by exchanging several types of communication objects:
- NMT (Network Management): Controls the state of CANopen devices (start, stop, reset).
- SDO (Service Data Object): Used for configuration and parameter access via a client-server model.
- PDO (Process Data Object): Transfers real-time I/O data efficiently, often using a producer-consumer model.
- Heartbeat/Node Guarding: Monitors device presence and network health.
The CANopen frame uses an 11-bit identifier (COB-ID) split into a 4-bit function code and a 7-bit node ID. This allows up to 127 nodes (ID 0 is reserved). With CAN 2.0B, 29-bit IDs can extend this limit. The arbitration mechanism ensures that lower COB-IDs have higher priority, making critical data like emergency messages or time-sensitive PDOs take precedence.
| Object Type | Function Code (Binary) | Typical COB-ID Range | Purpose |
|---|---|---|---|
| NMT | 0000 | 0x000 | Network management commands |
| Sync | 0001 | 0x080 | Synchronization for PDOs |
| Emergency | 0001 | 0x080 + Node ID | Device error alerts |
| PDO1 (tx) | 0011 | 0x180 + Node ID | Process data from slave |
| PDO1 (rx) | 0100 | 0x200 + Node ID | Process data to slave |
| SDO (tx) | 1011 | 0x580 + Node ID | Configuration response |
| SDO (rx) | 1100 | 0x600 + Node ID | Configuration request |
Profinet Interface
On the Profinet side, the gateway appears as a standard Profinet IO device. It supports real-time (RT) and sometimes isochronous real-time (IRT) communication. The gateway is configured using a GSDML file, which describes its modules and data structure. Key parameters include the device name, IP address, and the size of input/output data blocks that correspond to the mapped CANopen PDOs.
Configuration and Setup Process
One of the main advantages of a CANopen to Profinet gateway is its ease of configuration. Users typically do not need to write low-level code. Instead, setup involves defining parameters via configuration tools and EDS (Electronic Data Sheet) files.
Step-by-Step Configuration Outline
- Import GSDML file: Install the gateway’s GSDML file into the Profinet engineering tool (e.g., TIA Portal).
- Set Profinet parameters: Assign a unique device name and IP address to the gateway.
- Define I/O data lengths: Configure the number of input and output bytes that match the CANopen PDO mapping.
- Prepare CANopen configuration: Using the gateway’s own configuration tool or a text-based EDS file, specify the CANopen node IDs, PDO mappings, and communication parameters (baud rate, heartbeat, etc.).
- Load EDS files: Import the EDS files of the connected CANopen devices to automatically populate their object dictionaries.
- Map data: Link CANopen PDOs to the Profinet I/O slots. This is often done via a simple drag-and-drop or table-based mapping interface.
- Download and test: Transfer the configuration to the PLC and gateway. Upon power-up, the gateway automatically sends SDOs to configure the CANopen slaves and starts data exchange.
The gateway handles the initialization sequence: after establishing a Profinet connection with the PLC, it configures each CANopen slave via SDOs, sets up NMT states, heartbeat monitoring, and PDO parameters. Once configured, cyclic PDO data is transparently exchanged between the Profinet controller and the CANopen devices.
Typical Applications and Supported Devices
This gateway is used across various industries to integrate CANopen-based equipment into Profinet networks. Common devices include:
- Variable frequency drives (VFDs) and servo drives
- Power measurement devices and energy meters
- Intelligent sensors and actuators
- Remote I/O modules
- Encoders and motion controllers
- PLCs and DCS with CANopen interfaces
For example, in a packaging machine, a Profinet PLC can control multiple CANopen servo drives via the gateway, achieving coordinated motion while leveraging the diagnostics and speed of Profinet. Similarly, in process automation, CANopen temperature transmitters can be integrated into a Profinet-based DCS for monitoring and control.
Benefits and Considerations
Using a protocol gateway offers several advantages:
- Cost-effective integration: Avoid replacing existing CANopen devices.
- Simplified engineering: No need for custom protocol programming.
- Scalability: Easily add more CANopen nodes up to the network limit.
- Transparent data access: Process data appears as standard I/O in the PLC.
However, designers should consider the gateway’s performance limits, such as the maximum number of PDOs, cycle time, and supported CANopen features (e.g., dynamic PDO mapping). Proper network planning, including cable lengths and termination, remains essential for reliable operation.
Note: Always refer to the specific gateway’s user manual for detailed parameter ranges and compatibility. The configuration process may vary slightly between manufacturers, but the underlying principles of COB-ID mapping and EDS-based setup are standardized by CiA (CAN in Automation).
