CAN Transceiver Collision Detection via Propagation Delay
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing CAN bus protocols, particularly CAN XL, face challenges in reliable collision detection during the fast mode due to undefined bus voltage levels and signal reflections, which can lead to unreliable error frame detection and communication disruptions.
Innovation Solution
A CAN XL transceiver is designed to detect collisions by measuring propagation delays between signal edges and switching to a slow mode upon detection, ensuring reliable communication by maintaining timing symmetry and avoiding signal disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If CAN XL operates in fast mode with new voltage level scheme, then data transmission speed is improved, but collision detection reliability deteriorates due to undefined bus voltage levels and signal reflections
Solution Approach 1:
The transceiver measures the propagation delay between its own transmit signal and the corresponding receive signal, creating a feedback mechanism to detect collisions. When another node transmits simultaneously, the received signal pattern differs from the expected self-transmitted pattern, enabling reliable collision detection even in fast mode with new voltage levels
Solution Approach 2:
The patent replaces traditional voltage-level-based collision detection with a timing-based propagation delay measurement approach. Instead of relying on undefined voltage levels during fast mode, the system uses temporal measurement of signal edges to detect collisions, substituting electrical property detection with temporal property measurement
2Productivity
If CAN XL uses new voltage level scheme for fast mode, then communication efficiency is improved, but error frame detection becomes unreliable due to signal reflections
Solution Approach 1:
The system substitutes voltage-level-based error detection with timing-based propagation delay measurement. By measuring the time difference between transmit and receive signal edges, the system can reliably detect errors without being affected by signal reflections that plague traditional voltage-level detection in fast mode
3Measurement precision
If propagation delay measurement is performed for collision detection, then collision detection accuracy is improved, but device complexity increases due to additional timing measurement circuitry
Solution Approach 1:
The transceiver uses its existing transmit and receive signal paths for dual purposes: normal data communication and collision detection through propagation delay measurement. The same hardware components that handle data transmission are utilized to measure timing differences, eliminating the need for dedicated collision detection circuitry and reducing overall device complexity
Data Source
Figure 1a~1b
Figure 2
Figure 3~4
AI summary
The disclosure relates to a controller area network, CAN, unit and associated method and computer program. The CAN unit is configured to detect a transmit signal edge on a transmit signal for a CAN transceiver; detect a corresponding receive signal edge on a receive signal for a CAN controller of the CAN transceiver; and detect a collision on the CAN bus based on a propagation delay between the transmit signal edge and the corresponding receive signal edge.