OBD Bus Type Detection via Voltage Analysis
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Solution Overview
Problem
Current vehicle fault diagnosis methods face interference and instability due to different on-vehicle communications protocols, which affect bus communication data and diagnosis accuracy when scanning for bus types in sequence.
Innovation Solution
An OBD interface bus type detection method that determines the first bus feature of a connection cable associated with a selected pin, matches it with an OBD interface bus feature library, and sends the corresponding second bus feature to a diagnostic instrument to enable protocol scanning, reducing interference by matching the correct protocol for each bus type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sequential scanning of on-vehicle communications protocols is used to determine bus type, then all possible protocols can be detected, but communication data is seriously interfered with and diagnosis accuracy deteriorates
Solution Approach 1:
The patent applies preliminary action by detecting bus features (voltage levels, signal characteristics) before performing protocol scanning. The system pre-identifies the bus type by analyzing physical layer characteristics such as voltage ranges (e.g., 0-12V for K-line, 2.5-3.5V for CAN) and signal patterns, then selects the appropriate protocol for scanning. This prevents interference because the correct protocol is chosen upfront rather than attempting multiple protocols that could destabilize the bus.
Solution Approach 2:
The patent utilizes parameter changes by measuring and analyzing electrical parameters (voltage levels, current consumption, signal rise/fall times) to identify bus type. The system changes its detection approach from blind sequential protocol scanning to parameter-based bus characterization, where physical layer parameters dictate the subsequent communication protocol selection. This resolves the contradiction by making protocol selection dependent on measured parameters rather than fixed sequential scanning.
2Adaptability or versatility
If sequential protocol scanning is performed, then comprehensive protocol coverage is achieved, but scanning time and diagnostic efficiency are reduced
Solution Approach 1:
The system performs preliminary bus feature detection and analysis before protocol scanning to pre-determine the appropriate communication protocol. By characterizing the bus type upfront through voltage measurements and signal analysis, the system eliminates the need for time-consuming sequential scanning of multiple protocols, thus improving diagnostic efficiency while maintaining protocol compatibility.
Solution Approach 2:
The system uses the bus's own electrical characteristics (voltage levels, signal patterns, impedance) to automatically identify the correct protocol without requiring external intervention or manual configuration. The bus essentially identifies itself through its physical layer properties, enabling the diagnostic tool to select the appropriate protocol automatically and efficiently.
3Ease of operation
If K-line protocol scanning is used on CAN bus, then protocol scanning can be performed, but voltage is pulled up to 12V causing serious interference and instability
Solution Approach 1:
The patent applies parameter changes by measuring the bus voltage range and electrical characteristics to identify whether the bus is K-line (0-12V) or CAN (2.5-3.5V). Based on these measured parameters, the system dynamically selects the appropriate scanning protocol, preventing the harmful effect of applying 12V to a CAN bus which would cause interference and instability.
Solution Approach 2:
The system introduces an intermediary detection step that measures bus electrical parameters (voltage, impedance, signal characteristics) between the diagnostic tool and the actual protocol scanning. This intermediary measurement acts as a gatekeeper that determines which protocol can be safely applied, preventing direct interference by ensuring protocol compatibility before scanning begins.
Data Source
AI summary
The present invention provides an OBD interface bus type detection method and apparatus. The method includes: determining a first bus feature of a connection cable associated with a selected pin in an on-board diagnostics OBD interface; matching the first bus feature with an OBD interface bus library and determining a bus type of the connection cable associated with the selected pin; determining, according to the bus type of the connection cable associated with the selected pin, a second bus feature of the connection cable associated with the selected pin; and sending the second bus feature to a vehicle diagnostic instrument, to enable the vehicle diagnostic instrument to perform communications protocol scanning on the selected pin in the OBD interface according to the second bus feature. According to the present invention, a communications protocol meeting the second bus feature may be directly used by the vehicle diagnostic instrument to perform diagnostic scanning on the selected pin, thereby reducing scanning interference for different bus types.