CANopen vs CANopen FD | Key Differences & New Project Selection Guide

1. Industry Pain Points & Technical Evolution Background

Classic CANopen based on the traditional CAN bus has long been the mainstream communication protocol for industrial automation equipment such as PLCs, servo drives, and sensors. However, with the upgrading of intelligent manufacturing equipment towards multi-node, high-precision, and high-bandwidth iteration, traditional CANopen exposes increasingly prominent technical bottlenecks in new projects, bringing multiple engineering pain points:

• 8-Byte Payload Limit Causes Frequent Frame Fragmentation: Classic CANopen single PDO frames only support 8-byte effective data transmission. For complex equipment status data, multi-parameter sensor information, and servo operating data exceeding 8 bytes, multiple PDO frames are required for segmented transmission, which increases protocol overhead and bus collision probability.

• Single Baud Rate Leads to Insufficient Bandwidth: Traditional CANopen only supports a fixed single baud rate (max 1 Mbps). In multi-node dense networking scenarios, the bus load rate easily exceeds 80%, resulting in increased transmission latency, data jitter, and reduced synchronous control accuracy, failing to meet high-speed motion control demands.

• High Bus Load Reduces System Stability: Frequent small-frame fragmented transmission leads to sharp growth of bus message volume, long-term high-load operation of the bus, an increased error frame rate, and reduced real-time response capability of industrial control systems.

• Insufficient Compatibility for New Intelligent Equipment: New-generation high-precision servos, integrated multi-sensors, and edge industrial equipment support the CANopen FD high-speed protocol by default. Traditional CANopen cannot adapt to its large-data and low-latency transmission requirements, resulting in equipment function redundancy and performance waste.

• Unclear Selection Boundaries Lead to Project Performance Mismatch: Many new projects blindly inherit traditional CANopen solutions, resulting in insufficient system bandwidth reserves, or blindly adopt CANopen FD, causing unnecessary hardware cost waste in low-demand scenarios.

Against the background of intelligent industrial upgrading, CANopen FD, as an upgraded version of CANopen based on the CAN FD underlying architecture, solves the core limitations of traditional protocols in payload, transmission rate, and bus efficiency. Accurate distinction and scenario-based selection of the two protocols have become the key to optimizing the performance and cost of new industrial projects.

2. Core Technology & Underlying Architecture Difference Analysis

The essential difference between CANopen and CANopen FD comes from the underlying data link layer architecture. Classic CANopen runs on the standard CAN 2.0A/B physical layer, while CANopen FD is fully optimized based on the CAN FD flexible data rate architecture. It retains the complete CANopen object dictionary, PDO/SDO/EMCY protocol logic, and realizes comprehensive breakthroughs in payload capacity, transmission rate, and bus efficiency.

CANopen FD inherits all application layer protocols of classic CANopen, ensuring downward compatibility in protocol logic, while innovating a dual-rate transmission mechanism and ultra-long data frame payload, fundamentally solving the bandwidth bottleneck of traditional CAN bus industrial networking.

The following multi-dimensional parameter comparison table sorts out the core technical differences between the two protocols, providing accurate data support for new project engineering selection:

Core Technical Conclusion: The core upgrade of CANopen FD compared with classic CANopen lies in its 64-byte ultra-long payload and dual-rate high-speed transmission architecture. It retains all application layer protocol advantages of CANopen, solves the pain points of small payload, low throughput, and high bus load of traditional protocols, and is the standard technical solution for new high-performance industrial automation projects. Classic CANopen remains applicable only to low-bandwidth, low-frequency simple control scenarios.

3. Typical New Project Engineering Deployment Solutions

Solution 1: High-Precision Multi-Axis Servo Motion Control (CANopen FD Priority Scheme)

• Applicable Scenario: New intelligent automation production lines, multi-axis servo synchronous control equipment, and robotic arm joint control scenarios requiring high real-time performance, low jitter, and high synchronous precision with large servo operating parameter data volumes.

• Protocol Deployment Architecture: Adopt a standard CANopen FD protocol stack based on the CAN FD underlying architecture, enabling dual-rate transmission mode (arbitration segment 1 Mbps, data segment 5 Mbps). Utilize a 64-byte single-frame PDO to integrate servo position, speed, torque, and fault status multi-parameter data, eliminating traditional CANopen multi-frame fragmentation transmission, and optimizing bus scheduling timing.

• Actual Engineering Effect: The bus load rate is reduced from 82% (classic CANopen) to 35%, the control response latency is stably controlled within 5 ms, and the multi-axis synchronous error is reduced by 70%. Single-frame complete transmission of servo full parameters is realized, avoiding data synchronization errors caused by frame loss and delay of multi-frame transmission, fully meeting high-precision motion control requirements.

Solution 2: Low-Frequency Simple Industrial Control (Classic CANopen Cost-Effective Scheme)

• Applicable Scenario: New simple industrial monitoring equipment, single-node low-frequency switch control, and temperature and humidity single-parameter sampling scenarios with low data volume and low real-time requirements, pursuing low hardware cost and stable operation.

• Protocol Deployment Architecture: Deploy the classic CANopen protocol based on a standard CAN 2.0 bus, adopt a fixed 1 Mbps single baud rate transmission, match the 8-byte PDO small-data transmission mechanism, simplify protocol configuration, and retain basic PDO/SDO/EMCY functional logic to meet conventional control demands.

• Actual Engineering Effect: The hardware adaptation cost is reduced by 20% compared with the CANopen FD scheme, the protocol operation is stable and mature with no redundant performance overhead, the equipment debugging cycle is shortened, and it stably meets the operation requirements of simple low-bandwidth industrial control projects.

Solution 3: New and Old Equipment Hybrid Networking (CANopen FD Compatible Scheme)

• Applicable Scenario: Factory intelligent upgrading and reconstruction new projects that retain part of the traditional CANopen old equipment while adding new high-performance CANopen FD intelligent nodes, requiring hybrid compatible networking.

• Protocol Deployment Architecture: Take CANopen FD as the main protocol of the whole network, enabling downward compatibility mode. Old CANopen nodes access the network through the standard CAN 2.0 protocol, new FD nodes enable the 64-byte high-speed transmission mode, and the system unifies object dictionary parsing rules to realize seamless data interaction between new and old equipment.

• Actual Engineering Effect: Realizes zero-barrier hybrid networking of classic CANopen and CANopen FD equipment, avoiding full equipment replacement costs. The overall network operation stability rate reaches 99.99%, and the transmission efficiency of new equipment is improved by 5 times while retaining old equipment functions.

4. New Project Protocol Selection & Deployment Expert Best Practices

Based on extensive new industrial automation project debugging and deployment cases, follow these three core engineering specification guidelines for CANopen/CANopen FD selection:

1. Bandwidth Threshold Forced Selection Rule: For new projects with a single-node periodic data volume > 8 bytes or a bus node number $\ge$ 16 paired with high-frequency sampling ($\ge$ 100 Hz), CANopen FD must be adopted to avoid bus overload and data fragmentation. Projects with single-node data $\le$ 8 bytes and low-frequency control can stably choose classic CANopen to control costs.

2. Dual-Rate Parameter Matching Specification: When deploying CANopen FD, strictly distinguish the arbitration segment and data segment baud rate configurations. Fix the arbitration segment at 1 Mbps to ensure bus collision detection stability, and set the data segment to 3–5 Mbps according to data volume, avoiding communication errors caused by inconsistent dual-rate parameters.

3. Real-Time Control Scenario Optimization Strategy: High-precision synchronous control new projects must use the CANopen FD 64-byte integrated PDO transmission. Disable segmented SDO real-time transmission during operation to reduce bus message quantity and collision probability, ensuring system latency jitter stays $\le$ 5 ms to meet industrial high-precision control standards.

5. Frequently Asked Technical Questions (FAQ)

Q1: What are the core key differences between CANopen and CANopen FD for new projects?

A: The core differences lie in underlying bus capability and transmission efficiency. Classic CANopen is based on CAN 2.0 with an 8-byte maximum payload and a single 1 Mbps fixed baud rate, suitable for low-bandwidth simple control. CANopen FD is based on the CAN FD architecture, supporting a 64-byte ultra-long payload and 5 Mbps data segment high-speed transmission. This yields lower bus load and better real-time performance tailored to new high-performance industrial control projects.

Q2: Is it necessary to upgrade all new projects to CANopen FD?

A: No mandatory full upgrade is required. Simple low-frequency control, single-parameter monitoring, and low-cost miniature equipment new projects can retain classic CANopen to reduce hardware and development costs. Multi-parameter sampling, multi-axis synchronous control, high-frequency real-time interaction, and large-scale networking new projects must adopt CANopen FD to avoid performance bottlenecks.

Q3: Is CANopen FD fully backward compatible with traditional CANopen equipment?

A: Yes. CANopen FD retains complete CANopen application layer protocol and object dictionary specifications, supporting downward compatibility with classic CAN 2.0 CANopen equipment. It can realize hybrid networking of new FD nodes and old classic nodes on the same bus, making it well-suited for the phased upgrading of retrofitted projects.

Q4: What performance improvements can CANopen FD bring to multi-node industrial networking?

A: CANopen FD reduces bus load by 40%–60% through single-frame large-data transmission, solving the high load bottleneck of multi-node networking. The dual-rate high-speed mechanism reduces transmission latency by 70%+, effectively avoids data jitter and frame loss in high-frequency sampling scenarios, and greatly improves the stability and synchronous control accuracy of new industrial automation systems.