Active Stylus Downlink Timing Control for Sensor Controller Noise Reduction
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Solution Overview
Problem
In systems with liquid crystal panels, especially the in cell type, the sensor controller faces challenges in detecting signals from active styluses during display refresh periods due to noise interference, leading to potential data loss and delayed detection of pen down operations.
Innovation Solution
A method where the sensor controller acquires the current refresh cycle of the display panel and transmits an uplink signal for synchronization, allowing the active stylus to transmit downlink signals at designated times, thereby avoiding noise interference and ensuring timely detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the sensor controller continuously monitors for active stylus signals during display refresh periods, then the detection responsiveness is improved, but noise interference from liquid crystal driving signals causes detection accuracy to deteriorate
Solution Approach 1:
The sensor controller transmits uplink signals periodically at designated timing points that coincide with display refresh periods. The active stylus transmits downlink signals at these synchronized timing points, allowing the sensor controller to receive signals during periods when liquid crystal noise is minimal, thus maintaining both responsiveness and accuracy
Solution Approach 2:
The sensor controller transmits uplink signals in advance at designated timing points before the active stylus needs to respond. This preliminary action establishes a synchronization mechanism that allows the active stylus to transmit its downlink signals at optimal times, avoiding noise interference while maintaining detection responsiveness
2Measurement precision
If the sensor controller stops detection during display refresh periods to avoid noise, then detection accuracy is improved, but data loss increases due to missed stylus signals
Solution Approach 1:
Instead of stopping detection entirely during display refresh periods, the sensor controller uses periodic uplink signal transmission at designated timing points to maintain communication. This allows the system to filter out noise during most of the refresh period while capturing stylus signals at specific synchronized moments, reducing both noise interference and data loss
Solution Approach 2:
The uplink signal acts as an intermediary that synchronizes the communication between the sensor controller and active stylus. By using this intermediary signal transmitted at designated timing points, the system can distinguish between noise and valid stylus signals, reducing data loss while maintaining detection accuracy
3Device complexity
If the system uses a single sensor board for both touch detection and active stylus detection, then device complexity is reduced, but noise from liquid crystal driving signals worsens the detection reliability
Solution Approach 1:
The sensor controller uses periodic uplink signal transmission at designated timing points to separate touch detection and active stylus detection operations in time. This allows a single sensor board to perform both functions reliably by avoiding simultaneous operation during high-noise display refresh periods
Solution Approach 2:
The sensor controller transmits uplink signals in advance at designated timing points before active stylus detection is needed. This preliminary action establishes a timing framework that allows the single sensor board to perform touch detection during normal operation and active stylus detection during synchronized low-noise periods, maintaining reliability without adding hardware complexity
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 enables reliable and timely detection of active stylus signals, reducing data loss and improving the responsiveness of the system by synchronizing transmissions with minimal noise interference.
Implementation Method 1
The sensor controller supplies a transmission signal to an electrode group that configures a sensor board thereby to generate an electric field on a panel such that a signal can be transmitted toward the stylus
Implementation Method 2
The active stylus is configured such that it detects a variation of the charge amount induced in the electrodes by the electric field by the reception electrodes thereby to detect the signal transmitted from the electronic apparatus
Implementation Method 3
The voltage signal is used to control the orientation of the liquid crystal in each pixel, and enters an electrode group that configure the sensor board through alternating current (AC) coupling and makes noise
Data Source
AI summary
A method in which a sensor controller is connected to a sensor having an electrode group provided together with a display panel configured to operate in during a variable refresh cycle among a plurality of refresh cycles, and an active stylus performs bidirectional communication with the sensor controller. According to the method, the sensor controller acquires a present refresh cycle among the plurality of refresh cycles of the display panel, generates an uplink signal, which serves as a reference for synchronization corresponding to the acquired present refresh cycle, and transmits the uplink signal to the active stylus, which is not detected as yet or is detected already, at the present refresh cycle.