CANopen FD – enhanced features

CiA members demonstrated on the SPS IPC Drives tradeshow the capability of the USDO protocol.

CANopen FD demonstrator

A major task during updating the CANopen specification with regard to CAN FD has been the specification of the new communication object USDO. As most relevant aspects of the USDO communication object have already been specified, attendees of the SIG application layer offered their resources to setup a CANopen FD demonstrator for the SPS/IPC/Drives 2016 to illustrate the design flexibility of this new, powerful communication object.

The CANopen FD demonstrator integrates CANopen FD prototype implementations from the companies Emtas, ESD, HMS, and Microcontrol in a CAN FD system, using 500 kbit/s in the arbitration phase and 2 Mbit/s in the data phase. In parallel a second network based on classical CANopen integrates the nodes of the aforementioned companies as well.

Depending on the user interaction one node is triggering a request to the requested CANopen (FD) node either via pre-configured SDO communication or dynamically established USDO communication. Immediately after the successful completion of the request, the requested CANopen (FD) implementation starts to upload an illustration to the server, offered by the requesting node. The transfer of the data from the client to the server is running via that network, which provided the request, so either via CANopen or CANopen FD.

As the server starts immediately presenting the illustration on a display, the observer of the CANopen FD demonstrator can experience the rapid and flexible data transfer via CANopen FD’s USDO in comparison to the classical CANopen SDO. In case the data received via USDO, the data is much earlier available and can therefore much earlier be displayed in contrast to the data received via classical SDO.

Future CANopen FD application fields:

  • Applications dealing with increased security requirements, e.g. billing systems
  • Applications dealing with high amount of safety-relevant data, e.g. construction machineries
  • Applications that require robust and highly reliable communication, e.g. commercial vehicles
  • Applications with low energy consumption service, e.g. light-electric vehicles, service robots
  • All existing CANopen application fields suffering from a limited bandwidth or payload

The Universal Service Data Object (USDO)

Design flexibility by means of user

The USDO is intended to become the multi-function knife of embedded CANopen FD networking. The USDO is not just making use of the increased data throughput offered by CAN FD but adds a lot of useful functionality to CANopen FD.

In contrast to the classical SDO, the CAN-IDs used by the USDO do no longer determine the accessed (U) SDO server but the originator of an USDO request or response. To address a specific USDO server, the USDO client therefore has the task to code the intended USDO server in the data field of the request. Hence, the USDO client has the option to access one, several or all USDO servers available in the network at the same time. Furthermore the USDO client may have several sessions with the very same USDO server in parallel, e.g. to monitor the progress of a simultaneously running software download. As connectivity gets more and more important in times of the Internet of Things (IoT), the USDO provides an inherent routing capability. In heterogeneous network architectures, CANopen users just need knowledge about the topology (network- and node number) and they are enabled to access any CANopen device, connected to this network architecture. Additionally the USDO enables users to read and write multiple CANopen sub-indices by a single USDO access. The demonstrator provided at the CiA booth on occasion of the SPS/IPC/ Drives 2016 provides an insight to the CANopen FD design flexibility, added by the new USDO communication object.

USDO in principle
USDO attributes:

  • Dynamic access to any CANopen device by absence of a SDO manager
  • Accelerated, confirmed data transfer in uni-, multi-, and broadcast communication
  • Simultaneous USDO sessions between the very same USDO client and server
  • Access of several CANopen sub-indices by a single USDO access
  • Routing capability