CAN Bus Wake-Up Device Using Signal Edge Counting
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Solution Overview
Problem
Current bus systems, particularly in motor vehicles, face inefficiencies in waking up control units due to the need for separate wake-up lines or the unintended activation of all units via bus activity, leading to excessive power consumption and unnecessary wake-ups.
Innovation Solution
A method and device that utilize a counter to detect specified signal properties on the bus, allowing for selective wake-up by configuring edge counts in the arbitration and control fields of wake-up messages, enabling the use of different identifiers and reducing power consumption by switching off the clock generator before wake-up, allowing the bus signal to serve as the clock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all control units are woken up via bus activity, then communication can be established, but power consumption increases and unnecessary wake-ups occur
Solution Approach 1:
The wake-up mechanism is segmented into two independent stages: first stage detects signal properties (edges, levels) to determine binary information, second stage decodes the complete wake-up message. This segmentation allows partial processing in low-power mode while maintaining reliable communication.
Solution Approach 2:
The system performs preliminary detection of signal properties before full message decoding. By counting edges or detecting signal levels in advance, the system can determine wake-up candidates before activating the complete communication protocol, reducing overall power consumption.
2Adaptability or versatility
If separate wake-up lines are provided for all control units, then selective wake-up is achieved, but device complexity increases
Solution Approach 1:
The existing CAN bus is made multi-functional by enabling it to carry both normal communication data and wake-up signals. The same bus infrastructure serves dual purposes, eliminating the need for separate wake-up lines while maintaining selective wake-up capability through identifier-based addressing.
Solution Approach 2:
The wake-up message acts as an intermediary carrier that encodes both the wake-up command and the target identifier. This intermediary mechanism allows selective addressing without requiring separate physical lines, as the bus signal itself carries the selection information.
3Use of energy by moving object
If the clock generator is switched off to save power, then power consumption decreases, but wake-up processing becomes more difficult
Solution Approach 1:
The CAN bus signal itself serves as the clock source for the wake-up processing. By using the incoming bus signal's edges to synchronize the counter and signal property detection, the system eliminates the need for a separate clock generator during wake-up processing, reducing power consumption while maintaining accurate signal analysis.
Solution Approach 2:
The system uses periodic edge detection of the bus signal to advance through the wake-up processing stages. Each edge transition triggers the next detection phase, providing natural timing without requiring an external clock. This periodic action synchronized with the bus protocol reduces power consumption compared to continuous clock operation.
Data Source
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AI summary
The invention relates to a device for waking subscribers of a CAN bus system, characterized in that a detecting means, in particular a counter, is provided, detects at least one predefined signal property of the signals transmitted on the bus system, and, upon reaching a predefined count based on the signal property, introducing the further waking procedure, wherein the CAN bus itself uses the data flow as clock for recognizing the signal property.