Active Stylus Spread-Code Synchronization for Variable Uplink Timing

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Solution Overview

Problem

Existing bidirectional communication systems in touch-type input systems face inefficiencies due to uplink signals occupying communication resources, reducing the time available for downlink signals.

Innovation Solution

Implementing frame synchronization and variable-length commands in the communication protocol between an active stylus and a sensor controller, where the time length of uplink signals is adjusted based on the number of bits in the command, and using different spread codes for partial signals to optimize resource usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If bidirectional communication is implemented using time-division principles, then the stylus can be operated by commands from the sensor controller, but the communication time available for downlink signals is reduced

Engineering Contradiction:

Improvebidirectional communication capabilityVSAvoidcommunication time for downlink signals

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent applies dynamics by making the uplink signal duration variable rather than fixed. The sensor controller adjusts the uplink signal length dynamically based on the actual command size, allowing flexible time allocation between uplink and downlink communication phases

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of signal length from a fixed value to a variable value. By encoding the command length in the uplink signal itself, the system can adapt the time division ratio dynamically, ensuring efficient use of communication resources

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If fixed-length uplink signals are used, then the communication protocol is simple, but communication resources are wasted when commands are short

Engineering Contradiction:

Improvecommunication protocol complexityVSAvoidcommunication resource waste

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent changes the signal length parameter from fixed to variable, allowing the uplink signal to match the actual command size. This eliminates wasted communication resources while maintaining reasonable protocol complexity through self-contained length encoding

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Instead of always transmitting the full fixed-length signal, the system transmits only the necessary number of bits required for the command, avoiding excessive action when shorter commands are sufficient

Inventive Principle:

Principle #16Partial or excessive action

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 approach reduces the proportion of communication resources occupied by uplink signals, allowing for more frequent and efficient transmission of both uplink and downlink signals, thereby enhancing the overall communication efficiency.

Implementation Method 1

the sensor controller sends the first partial signal by way of direct spreading using a first spread code and sends the second partial signal by way of direct spreading using a second spread code

Methodology Applied

Scientific EffectDirect spreading:

Implementation Method 2

the active stylus is synchronized with the uplink signal by detecting the first partial signal using the first spread code and thereafter detects the second partial signal using the second spread code

Methodology Applied

Scientific EffectCorrelation detection:

Data Source

PatentUS12462672B2Method carried out in system including active stylus and sensor controller, sensor controller, and active stylus

Publication Date: 2025.11.04 WACOM CO LTD

AI summary

A sensor controller includes a transmitter configured to transmit an uplink signal including a first partial signal and a second partial signal. The transmitter is configured to transmit the first partial signal by direct spreading using a first spread code and transmit the second partial signal by direct spreading using a second spread code which is different from the first spread code and which has an identical chip time length to the first spread code. An active stylus includes a receiver configured to receive an uplink signal including a first partial signal and a second partial signal. The receiver is configured to synchronize with the uplink signal by detecting the first partial signal using a first spread code and thereafter detect the second partial signal using a second spread code, which is different from the first spread code and has an identical chip time length to the first spread code.