CAN Bus Termination Switching Using Device Identifiers
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Solution Overview
Problem
Existing CAN bus systems require separate manufacturing and assembly processes for end nodes with termination resistors, increasing complexity and cost, and external resistor connections complicate wiring harnesses.
Innovation Solution
Devices on the CAN bus include a switchable resistor and an interpreter circuit that uses device identifiers to determine if a device is an end node, automatically configuring the resistor to be connected or disconnected based on its ID, allowing identical device designs for all nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate manufacturing processes are used for end nodes with termination resistors, then signal integrity is maintained, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent implements a switchable termination resistor that can be dynamically enabled or disabled based on the device's role in the CAN bus network. The interpreter circuit reads the device identifier and automatically configures the termination resistor state, allowing identical hardware designs to function as either end nodes or middle nodes without separate manufacturing processes.
Solution Approach 2:
The patent changes the electrical parameter (termination resistance) based on the device identifier. The switchable resistor allows the termination parameter to be adjusted from enabled to disabled state according to whether the device is an end node or middle node, eliminating the need for different hardware configurations.
2Reliability
If external resistor connections are added to end nodes, then termination is achieved, but wiring harness complexity increases
Solution Approach 1:
The patent merges the termination resistor function into the device's internal circuitry rather than requiring external connections. The switchable resistor is integrated within the device, and the interpreter circuit controls its activation, eliminating the need for separate external resistor components and complex wiring harness connections.
Solution Approach 2:
The device performs its own termination configuration automatically. The interpreter circuit reads the device identifier and automatically enables or disables the integrated switchable resistor without requiring external wiring or manual configuration, making the system self-configuring.
3Ease of manufacture
If identical device designs are used for all nodes, then manufacturing is simplified, but automatic termination configuration is required
Solution Approach 1:
The device automatically determines its own configuration needs by reading its device identifier. The interpreter circuit autonomously decides whether to enable or disable the termination resistor based on the identifier, eliminating the need for manual configuration or separate manufacturing processes for different node types.
Solution Approach 2:
The device is pre-configured with a device identifier that encodes its role in the network. This preliminary identification allows the interpreter circuit to automatically determine the correct termination configuration without requiring post-manufacturing setup or external intervention.
Data Source
AI summary
A set of devices are coupled to a control area network (CAN) bus. At least some of the devices include switchable resistors that can apply a termination resistor to the CAN bus. Identification pins are used to identify devices on the CAN bus, and also to identify which device or devices are at the ends of the CAN bus. If a device is at an end of the CAN bus, the switch of the switchable resistor is set to couple the termination resistor to the CAN bus. Otherwise, the termination resistor is not coupled to the CAN bus.