CAN Bus Wake-Up Unit Selective Signal Decoding
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Solution Overview
Problem
Current CAN transceivers lack the ability to selectively switch individual participants to a sleep mode and wake them up only when specific messages or signal sequences are detected, leading to unnecessary power consumption and potential unwanted wake-ups during normal bus communication.
Innovation Solution
A three-stage process is implemented, where signal properties are counted in the first phase, time intervals between edges are measured in the second phase using an inaccurate oscillator, and the wake-up pattern is decoded in the third phase, ensuring unambiguous wake-up messages by using a synchronization pattern that prevents incorrect decoding in intermediate mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If transceivers continuously monitor the CAN bus for dominant bits to enable quick wake-up, then wake-up responsiveness is improved, but power consumption increases
Solution Approach 1:
The wake-up detection process is segmented into multiple phases: an initial phase where transceivers monitor the bus, and subsequent phases where only selected transceivers remain active based on detected signal properties. This segmentation allows the system to balance between quick wake-up responsiveness and reduced power consumption by having different transceivers active at different times.
Solution Approach 2:
The system dynamically adjusts which transceivers remain active based on the detected message type. When a wake-up candidate message is detected, the system transitions from a low-power state where most transceivers are inactive to an active state where specific transceivers monitor the bus further. This dynamic adjustment optimizes power consumption while maintaining wake-up responsiveness.
2Reliability
If transceivers wake up on any dominant bit detection to ensure no message is missed, then message detection reliability is improved, but selective wake-up capability deteriorates
Solution Approach 1:
The system performs preliminary analysis of signal properties (such as counting dominant bits or detecting specific patterns) before fully waking up transceivers. This preliminary action allows the system to determine whether a message is worth waking up for, thereby maintaining message detection reliability while enabling selective wake-up capability based on the preliminary assessment.
Solution Approach 2:
The patent introduces an intermediate detection mechanism that acts as a mediator between raw dominant bit detection and full transceiver wake-up. This intermediary layer analyzes message characteristics and selectively triggers wake-up only for relevant messages, thus preserving reliability while achieving adaptability.
3Speed
If transceivers remain in active mode to quickly detect messages, then detection speed is improved, but energy efficiency deteriorates
Solution Approach 1:
Instead of continuous active monitoring, the system employs periodic wake-up opportunities triggered by specific bus conditions. Transceivers alternate between low-power sleep mode and active monitoring mode based on detected signal properties, achieving energy efficiency while maintaining the ability to detect messages quickly when needed.
Solution Approach 2:
The system changes operational parameters (power state, monitoring intensity) based on detected bus conditions. When idle, transceivers operate in a low-power state with minimal monitoring. Upon detecting specific signal properties, they transition to full active mode for rapid message detection, thus optimizing both speed and energy efficiency dynamically.
Data Source
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AI summary
The invention relates to a method and a bus connection unit for selectively waking idle users of a bus system, wherein the non-idle users exchange messages via the bus using a serial communication protocol, wherein the messages are marked by a leading identifier, wherein the non-idle users decide on the basis of the identifier whether they receive the message, wherein the messages are evaluated by the idle users in at least three phases, wherein in a first phase a number of signal properties and/or edges and/or edge changes are determined, wherein in a second phase a sequence of time intervals between signal properties and/or edges and/or edge changes is determined, wherein in a third phase a wake pattern is determined from the serial signal sequence of the messages, and wherein idle users leave the idle state depending on the information determined during the at least three phases.