USB Port CAN Detection Using Pull-Up Voltage Sensing

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Solution Overview

Problem

Existing systems face challenges in efficiently routing Controller Area Network (CAN) traffic over Universal Serial Bus (USB) connections without requiring special USB port functions or circuitry in peripheral devices.

Innovation Solution

A method and device that determine whether a peripheral device is using CAN or USB by isolating it from the bus voltage line, connecting a USB signal line to a pull-up resistor, and measuring the digital value of the voltage to identify the protocol, allowing communication via USB or CAN without additional USB circuitry in the peripheral device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the host electronic device connects to a peripheral device using USB protocol, then communication compatibility is improved, but the ability to support CAN protocol without additional circuitry deteriorates

Engineering Contradiction:

Improvecommunication compatibilityVSAvoidUSB circuitry requirements

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The USB port is designed to support both USB protocol and CAN protocol through the same physical interface. The host electronic device can automatically detect which protocol is being used and configure the appropriate communication mode, making the USB port universal for both standard USB devices and CAN devices without requiring additional dedicated circuitry

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system changes communication parameters dynamically based on the detected protocol. When a CAN device is detected, the USB port operates in alternate mode with different electrical characteristics and signaling parameters compared to standard USB mode, allowing the same hardware to support multiple protocols

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If the host electronic device uses alternate mode signaling for CAN communication, then the need for additional USB circuitry is reduced, but the difficulty of detecting and measuring protocol type increases

Engineering Contradiction:

ImproveUSB circuitryVSAvoidprotocol detection

Core Design Contradiction:

Device complexityVSDifficulty of detecting and measuring

Solution Approach 1:

The host electronic device performs preliminary detection actions when a device is connected to the USB port. Before establishing full communication, the host sends test signals or queries that can identify whether the connected device is a USB device or a CAN device, allowing the system to prepare the appropriate communication mode in advance

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses an intermediary detection mechanism that facilitates protocol identification. This intermediary process acts as a mediator between the physical connection and the communication protocol selection, using voltage measurements or signaling responses to determine the appropriate protocol without requiring complex analysis

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the peripheral device is isolated from the bus voltage line during detection, then device safety is improved, but the measurement precision of voltage detection deteriorates

Engineering Contradiction:

Improvedevice safetyVSAvoidvoltage detection

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

A high-impedance measurement circuit or voltage divider acts as an intermediary between the bus voltage line and the detection circuitry. This intermediary allows the system to measure the voltage present at the USB port without directly connecting the measurement device to the power line, thus protecting sensitive components while still obtaining sufficient voltage information for protocol detection

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The detection circuit is designed with different impedance characteristics for different measurement points. The isolation mechanism creates a local measurement zone with high impedance that does not load the bus voltage line, allowing accurate voltage detection for protocol identification while maintaining device safety through proper electrical isolation

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables seamless communication between host and peripheral devices using either USB or CAN protocols, ensuring compatibility and reducing the need for special USB port functions in peripheral devices, thus maintaining compliance with USB standards.

Implementation Method 1

connecting a USB signal line to the bus voltage line via a pull-up resistor, and determining a digital value of a voltage of the USB signal line

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Data Source

PatentEP4411554B1Methods and devices for detecting a controller area network connection on a universal serial bus port

Publication Date: 2025.07.09 GEOTAB INC

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AI summary

A host electronic device (1600) that supports both Universal Serial Bus (USB) and Controller Area Network (CAN) connections is provided. The host electronic device (1600) drives at least one USB signal line and measures the voltage thereof. When the measured voltage indicates a USB connection from a peripheral device, the host electronic device (1600) determines that the peripheral device is a USB device. Otherwise, the host electronic device (1600) determines that the peripheral device is a CAN device.