CAN FD Light: Specification released

The nonprofit CiA (CAN in Automation) association has released the CiA 604-1 CAN FD Light specification as Draft Specification Proposal (DSP). This 16-page document describes CAN FD Light responder nodes. They only act on CAN FD data frames received from commander nodes. This avoids the need of costly add-on circuitry for the CAN FD Light responder nodes. The responder nodes do not arbitrate. The communication scheme is a commander/responder behavior. One commander node controls the communication of the connected responder nodes. The transmitted frames comply with the CAN FD data frames as specified in ISO 11898-1:2015. This means the maximum payload (data field) can be up to 64 byte. The sophisticated error detection features as specified in ISO 11898-1:2015 are supported, but error and remote frames are not transmitted. Therefore, the data frame scheduling should be periodical. This also means that there is no network-wide data consistency guaranteed. This should be solved in the application, if desired.

CAN FD Light is suitable for low-cost applications such as in smart headlights for road vehicles. The connected LED clusters can be controlled individually from one commander node. Other potential applications include heating, ventilation, and air-conditioning (HVAC) systems. In general, all simple sensor and actuator applications are addressed, especially in deeply embedded sub-systems. The CAN FD Light specification does not support bit-rate switching. Therefore, the maximum bit-rate is 1 Mbit/s, which is nevertheless faster than those used in traditional serial communication links (e.g. EIA 232) and networks (e.g. LIN).

The CiA 604-1 document will be accompanied by other CiA 604 series guidelines and application notes, which are under development. This open specification enables semiconductor suppliers to implement CAN FD Light responder nodes in their micro-controllers or in FPGAs (field programmable gate arrays). “CiA regards the CAN FD Light approach as a mayor step to improve price-sensitive deeply embedded networks,” said Holger Zeltwanger, CiA Managing Director. “Besides automotive applications, there is a huge potential for industrial sub-networks due to the robustness and reliability of the CAN FD communication.”