Smart Device Addressing on CAN Bus via Daisy Chain Verification
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Solution Overview
Problem
Existing methods for identifying and configuring multiple identical smart devices connected to a CAN bus face challenges such as increased costs, errors due to mislocation, and potential unsafe conditions caused by incorrect source addresses, particularly when harnesses corrode or fail, leading to incorrect function execution.
Innovation Solution
A system and method utilizing a daisy chain identification verification network separate from the CAN bus, where each smart device receives an identifier input signal, determines its source address based on a function instance value and factory default base address, and stores it in nonvolatile memory, allowing for automatic self-assignment and self-correction of location codes and source addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple identical smart devices are provided with different part numbers to identify locations, then location identification accuracy is improved, but inventory complexity and error risk increase
Solution Approach 1:
The patent segments the identification function into two parts: the physical device remains identical across all locations, while the location identification is achieved through the harness configuration and pin assignments. This separates the device identity from the location identification, allowing multiple identical devices to be used without requiring different part numbers.
Solution Approach 2:
The patent applies local quality by making the harness and pin configuration location-specific while keeping the smart device itself identical. Each location has its own harness configuration with specific pin assignments that identify the location, allowing the same device type to function correctly at multiple different locations without modification.
2Reliability
If different numbers of input pins are provided for each device to eliminate mislocation errors, then location identification reliability is improved, but connector size and cost increase
Solution Approach 1:
The patent implements universality by designing a standardized pin configuration where each smart device uses the same number of input pins, but the harness configuration at different locations assigns different pin combinations to identify different locations. This allows a single device design to work at multiple locations without requiring different numbers of pins.
Solution Approach 2:
The patent introduces the harness as an intermediary element that carries location identification information. Instead of modifying the device itself with different pin counts, the harness acts as a mediator that translates physical location into electrical signal identification through its configuration and pin assignments.
3Ease of operation
If in-harness resistors with different values are used for each location, then device self-identification is improved, but connection reliability and safety decrease due to corrosion or failure
Solution Approach 1:
The patent implements feedback by having the smart device read the resistance values from the harness during initialization, use this information to determine its location and assign itself a source address, and then store this configuration in non-volatile memory. This feedback loop ensures the device correctly identifies its location without relying on permanent physical modifications.
Solution Approach 2:
The patent applies preliminary action by having the device perform self-identification and source address assignment during the initialization phase before normal operation begins. The device reads the harness configuration, determines its location, assigns itself a source address, and stores this information in non-volatile memory before starting to function, ensuring reliability from the outset.
4Measurement precision
If a daisy chain identification verification network is implemented, then location verification accuracy is improved, but system complexity increases
Solution Approach 1:
The patent uses copying by having each smart device in the daisy chain receive and replicate the identification signal from the previous device. Each device copies the cumulative identification information from the harness configuration and uses it to verify its own location, creating a distributed verification system that enhances accuracy without requiring a centralized complex controller.
Data Source
AI summary
A system for communicating over a Controller Area Network (CAN) bus may include a central controller and a plurality of smart devices communicatively coupled with the central controller over the CAN bus and over an identification verification network separate from the CAN bus. Each smart device may be configured to at least one of measure various parameters and control a function based on a command received from the central controller, and then communicate one or more signals indicative of at least one of the measured parameters and the function over the CAN bus to the central controller. Each of the smart devices may include a physical input, a physical output, and at least two nonvolatile memory locations. A first of the at least two memory locations may be configured to store an identifier input signal received at the physical input from at least one of the central controller and an upstream smart device over the identification verification network, the identifier input signal being stored by the smart device as a function instance value for the smart device. The smart device may further include a source address determination module configured to determine a source address for the smart device based on the function instance value and a factory default base address for the smart device, and store the source address in a second of the at least two memory locations.