CANFD

CAN FD, short for Controller Area Network Flexible Data-rate, is an extension of the CAN protocol that enables larger data payloads and higher data rates during the data phase of a frame, while preserving the arbitration and control fields of classical CAN. It was developed by Bosch in 2012 to meet growing throughput needs in automotive and industrial networks and has since been incorporated into ISO CAN specifications to define its data link layer and compatibility with the CAN physical layer.

A CAN FD frame begins with the standard CAN arbitration and control fields. If the transmitter sets the Extended Data Length (EDL) and Bit Rate Switch (BRS) bits, the frame enters the CAN FD data phase, where the payload can be transmitted at a higher bitrate and up to 64 data bytes per frame. The data length code (DLC) in CAN FD maps to payload size, with values up to 64 bytes. The frame also employs an extended CRC (CRC-17) for the data phase, reflecting the larger payload. After the data phase, the frame concludes in the usual way and the bus returns to the nominal bitrate for the remainder of the transmission.

CAN FD increases network throughput and efficiency by reducing overhead and allowing larger messages, which is beneficial for applications such as software updates, sensor data batching, and control communications. While it preserves the basic CAN arbitration mechanism, full interoperability on a network requires that all nodes support CAN FD; older CAN-only devices may not correctly interpret CAN FD frames, limiting mixed-network operation.

CAN FD has found widespread use in automotive, industrial automation, and embedded systems where higher data payloads and faster data transfer improve performance.