CAN FD Frame Identifier Error Detection via Segmented Check Field
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Solution Overview
Problem
The CAN FD CRC generation mechanism is flawed, leading to incorrect identification of frame identifiers due to the CAN stuffing mechanism, particularly when the initialization vector is a zero vector, causing errors that are not detected by the CRC, resulting in communication issues between different implementations.
Innovation Solution
A method for serial transmission that inserts and removes stuff bits according to a predetermined rule, with additional information about the frame segment being transmitted outside the segment, allowing for verification of the frame's validity by comparing stored and received data, without modifying existing CAN FD controllers or initialization vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the initialization vector of the CRC generator is set to a zero vector, then the CRC generation is simplified and compatible with existing standards, but errors in frame identifiers caused by the CAN stuffing mechanism are not detected
Solution Approach 1:
The frame identifier is segmented into two parts: the original identifier bits and an additional check field. The check field is generated based on the identifier bits using XOR operations, creating a segmented structure that enables error detection without changing the core CRC mechanism
Solution Approach 2:
An intermediary check field is introduced between the identifier and the data payload. This check field acts as a mediator that validates the identifier reception before the main CRC check, preventing undetected errors from propagating through the system
2Reliability
If the initialization vector is changed to eliminate the CRC weakness, then error detection capability is improved, but compatibility between different CAN FD implementations is lost
Solution Approach 1:
Instead of changing the CRC initialization vector to fix the problem, the invention inverts the approach by adding a separate check field that operates independently of the CRC mechanism. This allows the CRC to remain unchanged and compatible while the check field provides the necessary error detection
Solution Approach 2:
The identifier bits are copied into a check field with the same bit width. This copy is then validated using XOR operations at the receiver, creating a redundant verification mechanism that does not interfere with the original CRC implementation
3Stability of the object's composition
If stuff bits are inserted according to the predetermined rule, then synchronization is maintained and frame boundaries are preserved, but identifier bits may be falsified without detection
Solution Approach 1:
The check field is generated in advance at the transmitter based on the identifier bits before the stuff bits are inserted. At the receiver, the check field is validated before the identifier is processed, preventing falsified identifiers from being accepted even if stuff bit insertion causes synchronization issues
Data Source
AI summary
The disclosure relates to a method for serially transmitting a frame from a transmitter to at least one receiver by means of a bus line, as well as a subscriber station for a bus system. According to said method, stuff bits are inserted into the frame by the transmitter according to a predetermined rule in order to generate additional signal edges, and/or said stuff bits are removed again by the receiver when evaluating the frame, at least one item of information relating to a subsection of the frame additionally being added, and transmitted, outside of this subsection, and said subsection containing a predetermined sequence of bit values.