Difference between CANFD and CANopen

Ⅰ. What is CANFD

CANFD is an extension of the classic CAN bus protocol proposed by Bosch in 2012, and was included in the ISO11898 1 standard in 2015, becoming an internationally accepted high-speed bus specification.
A traditional CAN single frame can only carry up to 8 bytes of data, while CANFD extends the maximum data length of a single frame to 64 bytes by introducing the EDL (Extended Data Length) field; at the same time, it can switch to a higher rate (BRS, Bit Rate Switching) (i.e. CANFD acceleration function) in the data phase, up to 5–8Mbps, to meet various high-speed demand scenarios. In order to ensure the transmission reliability of longer data frames, CANFD extends the CRC check length from 15/17 bits of classic CAN to 21 bits, further improving the error detection capability.
CANFD retains the multi-master mechanism, non-destructive arbitration, differential signal transmission and reliable error handling mechanism of classic CAN, ensuring backward compatibility and seamless integration into existing CAN networks.

Ⅱ. What is CANopen

CANopen is a communication protocol stack and device description specification based on the CAN bus, which is used for standardized interoperability between nodes in automated embedded systems. It not only defines the basic mechanism for data exchange, but also specifies the methods for device configuration and management. In the ISO/OSI model, CANopen implements the functions of the network layer and above (layer 3 to layer 7), relying on the underlying CAN bus to complete the data link and physical transmission. The six core concepts of CANopen are communication model, communication protocol, device state machine, object dictionary, electronic data sheet, and device configuration file. Each CANopen device contains an object dictionary, and all communication and application parameters are accessed through indexes and sub-indexes. The EDS (or XML-based XDD) file of the device describes the structure of the object dictionary, which facilitates automatic configuration and diagnosis by network management tools.

Ⅲ. The difference between the two

1.Protocol level

CANFD is an extension of the physical layer and data link layer of ISO11898 1 (classic CAN), which is used to define the frame format, rate switching and CRC mechanism; while CANopen is a high-level protocol (CiA301) based on classic CAN, which implements functions above the network layer (including network layer, transport layer, session layer, presentation layer and application layer), such as object dictionary, network management and PDO/SDO services.

2. Data load

CANFD introduces the EDL (Extended Data Length) field, which extends the maximum data load of a single frame from 8 bytes to 64 bytes; while traditional CANopen runs on the classic CAN bus, with a maximum of 8 bytes per frame. For larger data volumes, it needs to be transmitted in segments or multiple frames through SDO.

3. Transmission rate

In the arbitration phase, CANFD and classic CAN maintain 1Mbps; but in the data phase, it can be switched to 5–8Mbps (or even higher) through BRS (Bit Rate Switching), greatly increasing the bandwidth; while CANopen is limited to the maximum 1Mbps rate of the classic CAN bus.

4. Compatibility

CANFD is backward compatible with CAN2.0 and supports mixed transmission of classic CAN frames and FD frames in the same network; traditional CANopen (CiA301) nodes cannot recognize the CANFD frame format. If you want to run on a CANFD network, you need to upgrade to CANopenFD (CiA1301).

5. Application scenarios

CANFD is mainly used for scenarios with extremely high bandwidth and real-time requirements, such as large-capacity sensor data between modern automotive ECUs, OTA firmware updates, and high-speed industrial control; CANopen focuses on multi-node interoperability, standardized configuration and management, and is widely used in industrial automation, robotics, medical equipment, building control and other fields.