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CiA 309 series

Linking CANopen to TCP-based networks

Parts 1 to 3 of the CiA 309 TCP-gateway specification have been updated. Most of the changes are of an editorial nature, but some functional enhancements have also been included.

CiA 309 compliant gateways are not only embedded in subsea electronic modules on the ocean ground communicating with the CANopen transducers and the Ethernet-connected top-level controller, but are also increasingly used in industrial control systems (Photo: Aker Solutions)

EVERYONE IS TALKING ABOUT the Internet of Things (IoT). However, this concept is really just old wine in new wineskins. As early as 2004, CiA released the CiA 309 series of interface specification for CANopen-to-TCP gateways. Recently, the nonprofit association launched new versions for three parts of this set of specifications. Part 1 (version 2.0) describes the general principles and specifies the communication services. Besides some editorial improvements and corrections, the updated document provides a new section explaining CiA 309 operating sequences. It provides entire protocols, exchanged between a TCP device and a CANopen device, whereby the communication link is established via the CiA 309 gateway device.

The CiA 309 series also includes management services for gateway devices and CANopen host controllers. Other services are dedicated to initiating Layer Setting Services (LSS) in order to set the CANopen node-ID via the CAN network or to change the bit-rate. The related CiA 309 protocols are described in part 2 to part 4. Part 2, released as version 1.3, specifies ModbusTCP messages. The new CiA 309-2 document merely introduces some editorial improvements and corrections. Additionally, a Modbus extended exception has been introduced. Part 3 version 2.1 specifies the ASCII-based protocol and was launched at the end of July when the other parts has not been functionally extended. Only a few editorial changes were made including some additional definitions.

The CiA 309-4 gateway connects CANopen to ProfinetIO networks (Photo: ESD)

There are a few CiA 309 gateways on the market. Most of them use the ASCII-based protocols on the TCP-side. There are also software packages available providing the necessary protocol stacks for both interfaces as well as gateway programs (e.g. by Port and Emtas). They support ModbusTCP as well as ASCII protocols. In subsea applications, CiA 309 gateways are embedded in the so-called “tree”-controllers, which link the sensor networks on the ocean ground to the topside controller via TCP-based networks.

By means of the CiA 309 protocols, the user can access every device in the connected CANopen network from a remote controller. This TCP-connection is mainly used for remote configuration and remote diagnostic purposes. Real-time communication is done locally. Nevertheless, any CANopen device is a “thing” in the Internet via such a standardized CiA 309 compliant interface. “We have been doing this for more than 10 years,” explained Holger Zeltwanger, CiA’s managing director. “The first users came from the ModbusTCP business, followed by the generic ASCII protocol.” Additionally, the CiA 309-4 document specifies the remote access via ProfinetIO. CiA and Profibus International members have jointly developed this specification. Both associations already released it in the year 2011. ESD (Germany) was one of the first to implement this specification in its CANopen-to-ProfinetIO gateway.