Ring Topology Data Transmission for Automotive Serial Interfaces
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Solution Overview
Problem
Current serial interfaces, such as SPI, face challenges in transmitting time-critical actuation signals in automotive applications due to high latency, signal integrity issues, and poor EMC characteristics, especially at higher data rates, making them unsuitable for real-time safety applications.
Innovation Solution
A method and communications arrangement that utilizes a synchronous, bidirectional ring topology with continuous data transmission, encoding timing information within the data signal, and inserting stuffing or parity bits for timing recovery, allowing for low latency and phase-synchronous data transmission between participants, thereby improving signal integrity and reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If SPI interface is used for data transmission, then cost reduction and simplicity are achieved, but latency increases and real-time capability deteriorates
Solution Approach 1:
The patent implements a token passing mechanism where a token is circulated among participants in advance, allowing each participant to prepare and buffer data for transmission. This preliminary action enables deterministic latency by ensuring that data transmission can occur immediately when the token is received, without waiting for bus arbitration or protocol handshaking, thus resolving the contradiction between simplicity and real-time performance
Solution Approach 2:
The patent employs periodic token circulation around the ring bus, where the token is continuously passed from one participant to the next in a predetermined sequence. This periodic action creates a rhythmic, predictable transmission pattern that guarantees bounded latency while maintaining simple SPI-based communication, addressing the contradiction between interface simplicity and time-critical performance
2Speed
If data rate is increased in SPI bus topology, then transmission speed improves, but signal integrity and EMC characteristics deteriorate
Solution Approach 1:
The patent segments the data transmission into discrete packets that are transmitted in synchronization with the token circulation. Each packet is transmitted during a dedicated time slot when the token is present at that participant, breaking up continuous high-speed transmission into manageable segments. This segmentation reduces electromagnetic interference and signal integrity issues while maintaining overall high data rates through efficient parallel packet handling
Solution Approach 2:
The patent maintains continuous token circulation around the ring bus, ensuring that the transmission medium is constantly active with useful data traffic. By keeping the bus continuously occupied with synchronized packet transmissions rather than allowing idle periods or retransmissions, the system achieves high effective data rates while maintaining signal integrity through predictable, continuous operation
3Device complexity
If daisy-chain topology is used, then connection simplicity is achieved, but latency increases due to signal propagation delays
Solution Approach 1:
The patent merges the advantages of daisy-chain simplicity with ring topology efficiency by implementing a virtual ring using the existing daisy-chain physical connections. The token is passed through the daisy-chain structure, and each participant can transmit data immediately upon receiving the token without waiting for signals to propagate through the entire chain. This merging approach maintains connection simplicity while achieving low latency through the logical ring structure
Solution Approach 2:
The patent introduces a token as an intermediary that mediates data transmission in the daisy-chain topology. Instead of direct point-to-point communication that would require complex routing, the token acts as a mediator that grants transmission rights to each participant in sequence. This intermediary mechanism simplifies the control logic while enabling efficient data transmission with bounded latency
Data Source
AI summary
A method is described for transmitting data between participants of a serial, ring-shaped communications arrangement in which the participants are serially connected to one another, wherein a data packet is passed from a participant provided as a master to further participants provided as slaves, wherein the data packet is passed from slave to slave, and wherein address information of the data packet is altered by each slave.