CAN FD light – LED devices for passenger cars

CAN in Automation (CiA) has established a special interest group to develop a “handler/dog” data link layer protocol based on CAN FD. It is intended for use in sensor/actuator networks such as automotive lighting systems.

“Handler/dog” is a substitute term for “master/slave”. The nonprofit association develops a handler/dog data link layer based on the CAN FD protocol as specified in ISO 11898‑1:2015. The “handler” node implements the CAN FD protocol and sends just 11‑bit identifier FD frames. The “dog” nodes transmit data frames in FBFF (FD base frame format) only on request of the “handler” node. This avoids the implementation of high-performance and costly oscillators.

The protocol engine of the “dog” nodes is simplified compared to a CAN FD controller, explained the organization. Error and overload frames are not supported at all. Nevertheless, data fields of up to 64 byte are possible. The bit-rate is not switched and limited to one fixed value, for example 1 Mbit/s.

This commander/heeler approach is suitable for embedded networks in LED devices for passenger cars. Other application examples include door control subsystem and air‑conditionings with a lot of sensors. The CiA special interest group (SIG) is named “CAN FD light”. Fred Rennig from ST Microelectronics chairs the group, which comprises about 20 experts from different companies.

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