CAN Sample Point Detection via Recessive Bit Pulse Injection
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Solution Overview
Problem
The accurate configuration of the sample point in a CAN message is challenging due to its internal nature within the bit processing engine, making it difficult to determine if it is misconfigured, and existing mechanisms can mask errors, leading to potential misconfigurations in production.
Innovation Solution
A system that detects the start of a recessive bit in a CAN message, injects a dominant pulse at different locations within the bit period, and monitors the transmitting ECU's behavior to characterize and identify the sample point, allowing for correction if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the sample point configuration is made internal to the bit processing engine, then the device integration is improved, but the difficulty of detecting and measuring the sample point increases
Solution Approach 1:
The patent introduces an intermediary detection mechanism that injects test signals into the CAN bus and monitors the transmitting ECU's response. This intermediary approach allows external measurement of the internal sample point configuration by observing how the ECU reacts to injected dominant pulses during recessive bit periods, effectively bridging the gap between internal configuration and external detectability.
2Reliability
If existing error masking mechanisms are used, then the reliability of error handling is improved, but the ability to detect misconfigurations worsens
Solution Approach 1:
The patent applies preliminary action by performing sample point detection during the development and configuration phase, before the system is deployed to production. By injecting test pulses and characterizing the sample point location in advance, the system identifies misconfigurations before they can be masked by production error handling mechanisms, ensuring both detectability and reliability.
Solution Approach 2:
The patent implements feedback by monitoring the transmitting ECU's response to injected dominant pulses. When a pulse is injected during a recessive bit period, the system observes whether the ECU correctly responds by transitioning to dominant state. This feedback loop allows continuous verification of sample point configuration, enabling detection of misconfigurations that would otherwise be masked by error handling mechanisms.
3Adaptability or versatility
If the sample point location varies, then the adaptability to different configurations is improved, but the measurement precision of bit state determination worsens
Solution Approach 1:
The patent addresses parameter changes by systematically varying the injection timing of dominant pulses throughout the bit period. By injecting pulses at different time offsets and observing the ECU's response, the system characterizes the sample point location and determines the optimal injection timing that ensures accurate bit state sampling, thus maintaining precision despite configuration flexibility.
Data Source
AI summary
The transmission of a recessive bit in a CAN message from a transmitting electronic control unit (ECU) is detected, over a controller area network. A dominant pulse is injected onto the network after a delay time into the detected recessive bit. Behavior of the transmitting ECU is detected, and a sample point for the transmitting ECU is characterized based upon the detected ECU behavior. An action signal is generated based upon the characterized sample point.