CAN Bus Frame Extension for Higher Data Throughput
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Solution Overview
Problem
Current CAN bus systems face limitations in data transmission capacity and latency, particularly with increasing demands from modern vehicle systems, such as driving dynamics control and driver assistance systems, which require higher data volumes and faster transmission rates.
Innovation Solution
The method modifies the CAN bus protocol by allowing the data field to exceed the standard 8 bytes, with flexible interpretation of the data length code and use of modified CRC calculations, enabling larger data transmission while maintaining error detection security, and optionally switching bit lengths to enhance transmission speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the data field size is increased beyond 8 bytes, then the data transmission capacity is improved, but the compatibility with the CAN standard is worsened
Solution Approach 1:
The patent changes the interpretation parameters of the data length code (DLC) field in the CAN protocol. By reinterpreting the bit patterns of the DLC field, the system can distinguish between standard 8-byte data fields and extended data fields larger than 8 bytes, thereby increasing data transmission capacity while maintaining protocol compatibility through parameter redefinition
Solution Approach 2:
The patent introduces dynamic behavior in the CAN protocol by allowing the data field size to vary beyond the fixed 8-byte limit. The system dynamically adjusts the data field size based on the interpreted DLC values, enabling flexible data transmission lengths (e.g., 1-16 bytes or more) while maintaining backward compatibility with standard CAN controllers
2Productivity
If the average data transmission rate is increased, then the productivity is improved, but the error detection security may be worsened
Solution Approach 1:
The patent maintains continuous error detection security throughout the extended data field by applying CRC (Cyclic Redundancy Check) validation across the entire data field regardless of its size. The CRC mechanism operates continuously over the variable-length data field, ensuring that error detection capability is preserved even as data transmission rate and field size increase
Solution Approach 2:
The patent employs feedback mechanisms through acknowledgment fields and CRC check results that provide continuous verification of data integrity. The receiving station sends feedback regarding data validity, allowing the transmitting station to detect and retransmit erroneous data, thereby maintaining reliability despite increased transmission rates
3Adaptability or versatility
If flexible data field sizes are supported, then the adaptability is improved, but the device complexity is worsened
Solution Approach 1:
The patent segments the DLC field interpretation into distinct ranges or patterns, where different bit patterns correspond to different data field sizes. This segmentation approach allows the system to handle variable data lengths through structured, manageable interpretation rules rather than complex arbitrary logic, reducing implementation complexity while maintaining flexibility
Data Source
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AI summary
The invention relates to a method for the serial data transmission in a bus system with at least two participating data processing units. The data processing units exchange messages via the bus, and the transmitted messages have a logic structure in accordance with CAN standard ISO 11898-1, said logic structure comprising a start-of-frame bit, an arbitration field, a control field, a data field, a CRC field, an acknowledge field, and an end-of-frame sequence. The control field comprises a data length code that contains information on the length of the data field. The data field of transmitted messages can comprise more than eight bytes, deviating from CAN standard ISO 11898-1, and the values of the data length code are interpreted in a manner at least partly deviating from CAN standard ISO 11898-1 in order to determine the size of the data field.