Vehicle ECU Offloads Diagnosis to CAN Controller
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Solution Overview
Problem
The increasing CPU processing load and memory usage due to the expansion of software for failure diagnosis in vehicle control devices are causing a burden on the central processing unit, which needs to be reduced.
Innovation Solution
A vehicle control device is designed with a central processing unit that transmits execution instructions for failure diagnosis to a controller area network controller, which includes a storage unit and a sequencer to execute the diagnosis, reducing the burden on the CPU by offloading the diagnosis process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the central processing unit executes the failure diagnosis process directly, then the diagnosis can be performed, but the processing load and memory usage on the CPU increase
Solution Approach 1:
The failure diagnosis function is segmented from the central processing unit and assigned to a dedicated sequencer within the controller area network controller. This segmentation allows the CPU to focus on high-level control while the sequencer handles the detailed diagnosis execution, reducing CPU processing load and memory usage.
Solution Approach 2:
The controller area network controller acts as an intermediary between the CPU and the diagnosis target. It receives execution instructions from the CPU, performs the actual diagnosis through its sequencer, and returns results to the CPU, thereby offloading the diagnosis burden from the CPU.
2Adaptability or versatility
If software for failure diagnosis is expanded to cover more functions, then the diagnosis capability is improved, but the memory usage and processing load on the CPU increase
Solution Approach 1:
The diagnosis software and related data are extracted from the CPU's memory space and stored in the controller area network controller's memory. This extraction reduces the CPU's memory usage while maintaining expanded diagnosis capabilities through the dedicated controller's resources.
3Device complexity
If the central processing unit handles both control and diagnosis tasks, then the system structure is simple, but the processing load on the CPU increases
Solution Approach 1:
The system segments control functions (CPU) and diagnosis functions (controller area network controller) into separate processing units. This segmentation improves CPU processing efficiency by eliminating diagnosis-related overhead while maintaining a relatively simple overall system structure through the use of integrated controller functionality.
Data Source
AI summary
The vehicle ECU is a vehicle control device including a CPU and a CAN controller, wherein CPU transmits an instruction to execute a failure diagnosis to CAN controller, and CAN controller includes a diagnosis buffer storing data relating to a failure diagnosis request for the diagnosis target and data relating to a response from the diagnosis target, and a sequencer. The sequencer is configured to read data from the diagnosis buffers in response to reception of the execution instruction, transmit a failure diagnosis request to the diagnosis target ECU, receive a response transmitted from the diagnosis target ECU, perform diagnosis based on the response, and transmit the diagnosis result to CPU.