EmSA participated in the CANopen FD special interest group, which released a first version of CANopen FD (CiA 1301) in September. Benefits include up to 64 byte of data for TPDOs (the previous limit was 8 byte), plus an USDO mesh definition, whereby every node can send client requests to every other node.
Explaining the challenges of moving from CANopen to CANopen FD, Andy Ayre, EmSA’s CAN bus expert said:
“There are multiple protocol changes. The service data object (SDO) protocol has been completely replaced with Universal Service Data Object (USDO), a change that is not backwards compatible. Anyone familiar with CANopen will not understand the new USDOs unless there is high-level interpretation and the ability to generate the messages in order to test and access nodes. CANopen Magic provides all of that functionality.”
For those considering whether a move to CANopen FD is worthwhile, Ayre advises:
“SDOs are intended as point-to-point communication, however, there is a limit on the number of SDO channels available. In general, each node has one SDO channel which means it can only be accessed by one other node at a time. The traditional solution is to have a master that is the hub for all SDO communications, which is inefficient. With USDOs all of these problems are avoided. Any node can read from or write to another node without worrying about what other nodes are doing, making network design much more flexible. The other major advantage is that PDOs can now have up to 64 bytes of process data, resulting in more efficient transfer of real-time data on the network.”