CAN Bit Stream Sampling Using Dual-Edge Detection
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Solution Overview
Problem
Controller Area Network (CAN) bit stream sampling apparatuses face challenges in accurately detecting rising and falling edges due to signal distortions and asymmetries, leading to incorrect bit stream reconstruction and communication failures.
Innovation Solution
A CAN bit stream sampling apparatus that detects rising and falling edges separately and generates a restored non-return-to-zero coded bit stream, using oversampling to reject noise and synchronize edge detection based on both edges, allowing for accurate bit stream reconstruction even under high asymmetry conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional single-edge detection is used for bit stream sampling, then the device complexity is low, but the measurement precision of edge detection deteriorates under signal asymmetries
Solution Approach 1:
The sampling apparatus is segmented into two independent edge detection blocks: a first block for detecting rising edges and a second block for detecting falling edges. Each block independently processes one type of edge transition, allowing precise detection of both rising and falling edges without interference. This segmentation resolves the technical contradiction by improving edge detection precision through specialized dedicated circuits while keeping each individual block relatively simple in structure.
2Reliability
If oversampling is implemented to reject noise, then the reliability of bit stream reconstruction improves, but the loss of time increases due to multiple sampling cycles
Solution Approach 1:
The apparatus performs preliminary oversampling at multiple points within a bit period before final bit determination. By sampling multiple times in advance and comparing the samples, the system identifies valid edge transitions while rejecting noise-induced false edges. This preliminary action approach improves reliability by ensuring accurate edge detection even in noisy environments, while the time overhead is minimized through efficient sample comparison logic that quickly identifies valid edges.
3Measurement precision
If separate detection blocks for rising and falling edges are used, then the measurement precision of bit stream parameters improves, but the device complexity increases
Solution Approach 1:
The detection system is divided into two specialized blocks: one for rising edge detection and another for falling edge detection. Each block is optimized for its specific edge type, improving measurement precision for detecting bit transitions. The segmentation allows each block to use tailored detection logic and timing parameters appropriate for its edge type, achieving high precision while maintaining modular simplicity.
Solution Approach 2:
Despite the separate blocks, both edge detection blocks share common functionality for nominal bit time determination and synchronization. The apparatus uses a unified approach to calculate bit boundaries and synchronize sampling based on detected edges, allowing the system to handle both rising and falling edges through a common control mechanism. This multi-functionality reduces overall complexity by avoiding complete duplication of all detection logic.
4Adaptability or versatility
If synchronization based on both rising and falling edges is implemented, then the adaptability to signal asymmetries improves, but the difficulty of detecting and measuring edges increases
Solution Approach 1:
The system segments edge detection into two independent specialized blocks, each optimized for detecting one type of edge transition. This segmentation simplifies the detection task for each block, making it easier to detect and measure edges while improving adaptability to signal asymmetries. Each block can independently determine nominal bit times and synchronize sampling based on its detected edges without being affected by the other edge type.
Solution Approach 2:
The apparatus dynamically adapts its detection parameters based on the detected edges. When a rising edge is detected by the first block, the system adjusts sampling synchronization accordingly; when a falling edge is detected by the second block, it similarly adjusts. This dynamic adaptation to the actual signal characteristics improves versatility in handling asymmetric signals while keeping the detection logic simple through event-driven parameter adjustment.
Data Source
AI summary
A Controller Area Network, CAN, bit stream sampling apparatus for a CAN controller, the apparatus configured to receive a bit stream from a CAN transceiver, the apparatus configured to:detect rising edges in said bit stream;detect, separately, falling edges in said bit stream; andgenerate a restored non-return-to-zero coded bit stream based at least on said detected falling edges and said detected rising edges.