Bus System Addressing via Current Source Pre-Selection
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Solution Overview
Problem
Existing bus systems face challenges in reliably assigning unique addresses to addressable participants under variable conditions of supply voltage and participant count, leading to errors in address allocation, especially in automotive environments with devices from multiple vendors.
Innovation Solution
A method utilizing pre-selection and selection currents provided by current sources independent of the supply voltage, with specific threshold values calculated to ensure each participant is assigned a unique address, using a first and second threshold to guarantee accurate address allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If current sensing methods are used for address allocation, then automation is improved, but measurement precision deteriorates under variable supply voltage conditions
Solution Approach 1:
The patent replaces voltage-based sensing with current-based sensing using a shunt resistor. By measuring current through the shunt rather than voltage levels, the system achieves supply voltage independence. The current measurement via shunt resistor 32 provides a stable reference that is not affected by variations in supply voltage, thereby maintaining measurement precision while preserving automation.
Solution Approach 2:
The patent changes the measurement parameter from voltage to current. Instead of sensing voltage levels that vary with supply voltage, the system measures current flow through the shunt resistor. This parameter change makes the measurement invariant to supply voltage variations, solving the precision problem while maintaining automated address allocation.
2Device complexity
If pull-up resistors are used for current sensing, then device complexity is reduced, but manufacturing precision deteriorates due to tolerance variations
Solution Approach 1:
The patent introduces a shunt resistor as an intermediary sensing element placed in the current path. This shunt resistor provides a stable, low-value resistance that creates a predictable voltage drop proportional to current. Unlike high-value pull-up resistors subject to tolerance variations, the shunt resistor's small value and precise placement make it less sensitive to manufacturing tolerances, improving manufacturing precision while keeping the circuit relatively simple.
3Reliability
If sequential addressing is used, then reliability is improved by ensuring unique addresses, but productivity decreases due to time-consuming addressing process
Solution Approach 1:
The patent employs feedback mechanisms where each participant monitors the current on the bus and compares it against expected values. Participants iteratively adjust their addressing logic based on feedback from current measurements, allowing them to self-configure their addresses. This feedback-driven approach ensures unique address assignment (reliability) while enabling parallel convergence of addresses across multiple participants (productivity).
Solution Approach 2:
The system performs preliminary current measurements and calculations before final address assignment. Participants pre-calculate their addresses based on initial current readings and iteratively refine their assignments. This preliminary action allows the system to converge on unique addresses more efficiently, improving both reliability and productivity by avoiding repeated trial-and-error cycles.
Data Source
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AI summary
A robust method for addressing each of the participants of a bus system (110) comprising a control unit (112), and a bus (114) and a plurality of addressable participants (116) connected to the bus, comprising the steps of a) pre-selecting a first number (N1) of participants, b) selecting from the pre-selected participants a second number (N2) of participants, and c) assigning one or more addresses to them, and repeating the steps a) to c). The selection and pre-selection is based on current sources (CS1, CS2), specific threshold values (T1-T4), and measurement error (Emax). The bus system (110) and addressable device (116) are also claimed.