CANopen FD under development

The CANopen SIG application layer develops the CANopen FD specification. It will introduce a new SDO protocol, called USDO (Universal SDO).

The CANopen FD application layer will use only CAN FD frames. The CANopen SIG allocation layer chaired by Dr. Martin Merkel from HMS doesn’t intended to change the NMT, Boot-up, Heartbeat, TIME, SYNC, and EMCY protocols. The PDO protocol will make, of course, use of the longer payload (up to 64 byte) provided by the CAN FD frames. The two PDO parameter sets will not be changed. This means, there are just 64 PDO mapping entries. A bit-wise mapping of process data restricts the PDO length. In order to use the maximum payload a byte-wise mapping is necessary.

The most significant improvement is regarding the SDO protocol. The newly introduced USDO protocol enables a DAM MPDO alike addressing with fully meshed communication coherences, in multi- or broadcast communication relations. In contrast to classical SDOs, complex proprietary SDO server channel access management becomes therefore obsolete. Global addressing information may be communicated within the USDO. Therefore CANopen FD devices are best equipped for the challenges of IoT, because of the inherent USDO routing capability. Consequently, complex additional routing protocols are avoided. Furthermore the SIG application layer intends to accelerate the up- and download of CANopen object dictionary entries by introducing accessing entire Arrays or Records with a single USDO service.

The CANopen FD protocol will be launched as Draft Standard Proposal by end of this year. In parallel, the CANopen conformance test plan needs to be reviewed. In the future, a CANopen FD conformance test will be mandatory, in order to guarantee a high quality of CANopen devices.

Detailed information about the current status of the CANopen FD specification development is available from CiA. Please email your questions to