USB Device Role Detection Without ID Pin Using Data Line Resistors
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Solution Overview
Problem
Existing USB devices require an ID pin to determine whether they are master or slave devices, occupying a valuable resource and limiting their functionality.
Innovation Solution
A USB device design that uses a combination of pull-up and pull-down resistors and switches on the D+ and D− data lines, along with a VBUS drive control module, to detect the device role without an ID pin, allowing for automatic determination of the device's role as master or slave based on the voltage levels on these lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an ID pin is used to detect device role, then the detection accuracy is improved, but the pin resource consumption increases
Solution Approach 1:
The invention extracts the device role detection function from the dedicated ID pin and relocates it to the existing D+ and D− data lines. By removing the requirement for the ID pin while maintaining detection capability through the data lines, the solution reduces pin resource consumption without sacrificing detection accuracy
Solution Approach 2:
The invention makes the D+ and D− data lines serve dual purposes: they function as data transmission lines for USB communication and simultaneously serve as detection lines for device role identification. This multi-functionality eliminates the need for separate dedicated detection pins, thereby saving pin resources while maintaining accurate device role detection
2Quantity of substance
If multiple pull-up and pull-down resistors with switches are added, then the device complexity increases, but the pin resource savings offset this complexity
Solution Approach 1:
The invention merges the device role detection circuitry with the existing USB data transmission circuitry. The pull-up and pull-down resistors with switches are integrated into the D+ and D− lines that already carry data signals, combining detection and communication functions into a unified circuit structure
Solution Approach 2:
The invention introduces controllable switches that dynamically connect or disconnect the pull-up and pull-down resistors based on the detected device role. This dynamic configuration allows the circuit to adapt its state during operation, enabling flexible role switching between master and slave while managing circuit complexity through controlled activation
3Quantity of substance
If the detection is performed without an ID pin, then the pin resource is saved, but the detection reliability may be affected
Solution Approach 1:
The invention implements a feedback mechanism where the detection circuit continuously monitors the voltage levels on D+ and D− lines and adjusts the switch states accordingly. The controllable switches respond to detected voltage patterns by connecting or disconnecting resistors, creating a feedback loop that ensures reliable and accurate device role detection without requiring an ID pin
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
This solution enables the detection of USB device roles without using the ID pin, thereby saving a pin resource and maintaining performance, while ensuring accurate identification of device roles without concurrent detection issues.
Implementation Method 1
a first pull-up resistor, a second pull-up resistor, a third pull-up resistor... a fourth pull-down resistor, a fifth pull-down resistor... when the first pull-up resistor and the fourth pull-down resistor on the D+ data line are switched on concurrently, a voltage on the first pull-up resistor is in a range of logically low levels
Data Source
AI summary
A USB device and a detection method therefor. It can be detected whether the USB device is a master device or a slave device without the use of an ID pin, thereby saving the pin resources of the USB device. The USB device comprises: a series branch formed by a first pull-up resistor (R1) and a first switch (S1) and having one end connected to VCC and the other end connected to a D+ or D− data line; a series branch formed by a second pull-up resistor (R2) and a second switch (S2) and having one end connected to the VCC and the other end connected to the D+ data line; a series branch formed by a third pull-up resistor (R3) and a third switch (S3) and having one end connected to VCC and the other end connected to the D− data line; a series branch formed by a fourth pull-up resistor (R4) and a fourth switch (S4) and having one end being grounded and the other end connected to the D+ data line; and a series branch formed by a fifth pull-up resistor (R5) and a fifth switch (S5) and having one end being grounded and the other end connected to the D− data line. The USB device belongs to the field of communication devices.