CAN Bus Data Field Adaptation for Extended Transmission
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Solution Overview
Problem
Current CAN bus systems are limited by a maximum data field size of eight bytes, which restricts data transmission capacity and flexibility, especially in modern vehicle networks requiring increased data quantities and reduced latency.
Innovation Solution
The method allows for data fields larger than eight bytes by modifying the data length code interpretation and using additional buffer memory, enabling flexible data transmission while maintaining compatibility with standard CAN systems through identifiers and checksum adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the data field size is increased beyond eight bytes, then the data transmission capacity is improved, but the compatibility with standard CAN systems deteriorates
Solution Approach 1:
The system dynamically adapts its data field size based on the communication mode. In normal CAN mode, it maintains 8-byte data fields for compatibility. In extended mode, it can utilize larger data fields when needed, allowing the system to flexibly switch between compatibility and enhanced capacity requirements
Solution Approach 2:
The invention changes the interpretation of the data length code parameter to support larger data field sizes. By redefining how the DLC field is interpreted and utilizing additional buffer memory beyond the standard 8 bytes, the system can transmit larger data quantities while maintaining the same message structure format
2Adaptability or versatility
If additional buffer memory is provided for larger data fields, then the data transmission flexibility is improved, but the device complexity increases
Solution Approach 1:
The buffer memory is designed to serve multiple purposes: it functions as standard 8-byte CAN buffer for compatibility mode, and can be expanded to handle larger data fields when needed. This multi-functional design allows the same hardware resource to support both standard and extended operation modes without requiring separate dedicated memory for each mode
3Loss of time
If the data field size is enlarged, then the latency time is reduced, but the manufacturing complexity increases
Solution Approach 1:
The communication controller is pre-configured with extended buffer memory capacity and the capability to interpret DLC fields for larger data sizes. This preliminary preparation allows the system to immediately handle large data transmissions when needed, reducing latency without requiring runtime reconfiguration or additional manufacturing complexity for optional features
Data Source
AI summary
A method is described for serial data transmission in a bus system having at least two participating data processing units, the data processing units exchanging messages via the bus, the sent messages having a logical structure in accordance with CAN standard ISO 11898-1. When a first changeover condition is present, then, deviating from CAN, the data field of the messages can include more than eight bytes, the values of the data length code being interpreted, given the presence of the first changeover condition to determine the size of the data field. For forwarding data between the data field and the application software, at least one buffer memory is provided, and, if the size of the data field differs from the size of the buffer memory used, the forwarded quantity of data is adapted at least corresponding to the difference in size between the data field and the buffer memory.