JTAG Interface Single-Wire Bus Automotive LED Control
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Solution Overview
Problem
Current methods for controlling automotive LED light strips require multiple lines for data transmission, including a supply voltage line, ground line, clock line, signaling line, and data line, leading to increased costs and weight, and lack a return channel for error detection and self-testing, making them inefficient for automotive applications.
Innovation Solution
A single-wire data bus system using a JTAG interface with time-multiplexed signals and multiple voltage ranges allows bidirectional data transmission between a bus master and multiple bus nodes, reducing the number of physical connections needed and enabling error detection and self-testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple lines (supply voltage, ground, clock, signaling, data) are used for controlling LED light strips, then reliable control and power supply are achieved, but the number of connections increases leading to higher costs and weight
Solution Approach 1:
The patent combines multiple functions (data transmission, clock signaling, and bidirectional communication) into a single data bus line. The JTAG interface enables the single wire to carry both control signals from the bus master to bus nodes and feedback signals from bus nodes to the master, eliminating the need for separate supply voltage, ground, clock, and signaling lines while maintaining reliable control through protocol-level error detection and acknowledgment mechanisms.
Solution Approach 2:
The single data bus line serves multiple functions simultaneously: it transmits data from master to slaves, carries clock signals, provides feedback channels for error detection, and enables bidirectional communication for self-testing. The JTAG protocol allows the same physical medium to perform what previously required five separate lines, reducing wiring complexity while preserving control reliability through multi-functional signal encoding.
2Weight of stationary object
If a single data line is used for bidirectional transmission, then the number of connections is reduced, but the complexity of signal multiplexing and voltage range management increases
Solution Approach 1:
The patent utilizes multiple voltage ranges (first voltage range for logic low, second voltage range for logic high, third voltage range for intermediate states) to encode different signal states and control directions. By changing voltage parameters dynamically, the system achieves bidirectional communication and signal multiplexing on a single wire without requiring complex mechanical switches or additional control lines, managing the complexity through electrical parameter variation rather than structural complexity.
3Ease of manufacture
If traditional control methods are used, then simple implementation is achieved, but no feedback channel exists for error detection and self-testing
Solution Approach 1:
The JTAG interface implements a feedback mechanism where bus nodes send acknowledgment signals and error status information back to the bus master through the same data bus. The master can detect transmission errors, verify node functionality, and initiate self-testing procedures by sending test patterns and analyzing returned data, providing a complete feedback loop for error detection and system reliability without adding separate feedback wiring.
Data Source
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AI summary
The JTAG interface of a bus node (BS1, BS2, BS3) for controlling at least one actuation device of at least one lighting means using a bus node (BS1, BS2, BS3) of a lighting chain comprises at least one illumination register (ILR) as a data register (DR) of the JTAG interface, wherein the actuation of the lighting means using the bus nodes (BS1, BS2, BS3) depends at least temporarily on the at least temporary content of the illumination register. The JTAG interface is characterized in that the test controller (TAPC) comprises a state diagram according to the IEEE 1149 standard and in particular one or more of the sub-standards IEEE 1149.1 to IEEE 1149.8 and the developments thereof.