CAN Bus Protocol Flexible Message Size Variable Bit Length
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing serial data transfer methods in CAN bus systems are inadequate for handling increasing data volumes and latency demands in modern vehicle networking, particularly for applications like vehicle dynamics control and driver assistance systems, as they restrict data field size and bit length, limiting data transfer efficiency and reliability.
Innovation Solution
The method introduces a modified CAN bus protocol that allows for a data field size exceeding 8 bytes and variable bit lengths using additional markers (EDL and BRS) within the control field, enabling flexible data transfer and error detection while maintaining compatibility with standard CAN controllers, allowing for larger data fields and enhanced fault tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the data field size is limited to 8 bytes as per CAN standard, then compatibility with standard CAN controllers is maintained, but data transfer capacity is insufficient for modern vehicle networking demands
Solution Approach 1:
The patent changes the parameter of data field size from the standard 8-byte limit to variable sizes (16, 32, or 64 bytes) by modifying the interpretation of the Data Length Code (DLC) field. When the EDL marker is present, the DLC values are reinterpreted to indicate extended data lengths, enabling larger data payloads while maintaining protocol compatibility.
Solution Approach 2:
The patent segments the control field by introducing a marker bit (EDL) that divides the message structure into standard CAN portion and extended CAN FD portion. This segmentation allows standard CAN controllers to process the initial part of the message while extended functionality is activated only when the marker is detected, enabling gradual adoption and backward compatibility.
2Productivity
If variable bit lengths are implemented to increase data transfer rate, then productivity is improved, but device complexity increases due to additional markers and protocol modifications
Solution Approach 1:
The patent changes the bit length parameter dynamically within the message stream by introducing the BRS (Bit Rate Switch) marker. When BRS is detected, the bus switches to a shortened bit length for the data portion, increasing transfer rate. The bit length returns to normal after the CRC delimiter, allowing variable speed transmission without permanent system modification.
Solution Approach 2:
The patent makes the bit length dynamic rather than static by implementing rate switching capability. The system can adaptively change the bit length during message transmission based on the BRS marker, allowing faster data transfer when needed while maintaining standard timing elsewhere. This dynamic adjustment optimizes productivity without permanently increasing complexity.
3Adaptability or versatility
If the control field is extended to include additional markers, then adaptability is improved, but manufacturing precision deteriorates due to deviations from ISO 11898-1 standard
Solution Approach 1:
The patent segments the control field into standard CAN portion (first 6 bits) and extended CAN FD portion (additional bits). The additional bits are used as markers (EDL, BRS, ESI) that provide extended functionality. This segmentation allows the message to conform to ISO 11898-1 for the standard portion while adding optional extended features, maintaining manufacturing precision for standard compliance while improving adaptability.
Solution Approach 2:
The patent makes the control field universal by designing it to serve both standard CAN and extended CAN FD functions. The same control field structure is used for both protocol versions, with the additional bits providing enhanced functionality when activated by the EDL marker. This multi-functionality allows a single message format to satisfy both standard compliance requirements and extended capability needs.
Data Source
AI summary
A method for serial data transfer in a bus system having at least two bus subscribers that exchange messages via the bus, the transmitted messages having a CAN standard ISO 11898-1 structure, where for a first marker (EDL), the control field of the messages, divergently from ISO 11898-1, encompasses more than 6 bits, and for the EDL, the data field of the messages, divergently from ISO 11898-1, may encompass more than 8 bytes, the values of the 4 bits of the data length code being interpreted divergently from ISO 11898-1 to establish the data field size, and for a second marker (BRS), the bit length for at least one predefined or predefinable region within the message assumes a value that is shortened as to the bit length used before the second marker was present, the region beginning at the earliest with the second marker and ending at the latest with the CRC delimiter, and the BRS occurring only when the EDL is present, and occurring in the control field of the messages which encompasses more than 6 bits.