Active Stylus Detection via Dynamic Blanking Period Timing
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Solution Overview
Problem
Existing display controllers face a reduction in display quality due to fixed blanking periods, leading to visually observable horizontal lines and sounding, as they cannot change the position of the blanking period without occupying additional data transmission space with auxiliary uplink signals.
Innovation Solution
The active stylus transmits the same packet multiple times within a display frame, allowing the display controller to arbitrarily change the blanking period without using auxiliary uplink signals, and the display controller adjusts the start and end timings of the display driving period while maintaining set time intervals between packet transmission periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an auxiliary uplink signal is transmitted in each blanking period to notify the active stylus of the blanking period position, then the display quality is improved by enabling accurate blanking period notification, but the data transmission capacity is reduced because part of the blanking period is occupied by the auxiliary signal
Solution Approach 1:
The active stylus transmits the same packet multiple times within a single display frame during different blanking periods. This copying approach allows the display controller to receive identical data packets at different timing positions, enabling the controller to adjust blanking period positions without requiring additional auxiliary uplink signals, thus maintaining data transmission capacity while improving display quality
Solution Approach 2:
The pen signal packets serve multiple functions: they carry both the data transmission function and the timing reference function for blanking period notification. By making the pen signals universal, the system eliminates the need for separate auxiliary uplink signals, preserving data transmission capacity while enabling flexible blanking period positioning
2Device complexity
If the position of the blanking period is fixed for multiple frames until re-notification is possible, then the uplink signal resource is saved, but display quality deteriorates due to discontinuous display driving operation causing horizontal lines and sounding
Solution Approach 1:
The display controller dynamically adjusts the position of blanking periods within each display frame by selecting different timing positions for receiving pen signal packets. This dynamic adjustment enables continuous and smooth display driving operation across multiple frames, eliminating horizontal lines and sounding while maintaining simple signal transmission without frequent auxiliary uplink signals
3Adaptability or versatility
If the same packet is transmitted multiple times within a display frame, then the display controller can change blanking period position without auxiliary signals, but the transmission time increases
Solution Approach 1:
The active stylus transmits the same packet at periodic intervals during different blanking periods within a single display frame. This periodic transmission approach allows the display controller to receive the packet at multiple timing positions, enabling flexible blanking period positioning while keeping the total transmission time within acceptable limits by utilizing otherwise idle blanking periods
Data Source
AI summary
A method in a system including an active stylus and a display controller that detects the active stylus and that drives a display device. The method includes: driving the display device to display first pixel data during a first display period in a first time period, wherein the driving is started a first amount of time and ended a second amount of time after the beginning of the first time period; and driving the display device to display second pixel data during a second display period in a second time period, wherein the driving is started a third amount of time and ended a fourth amount of time after the beginning of the second time period. The first and second display periods have a same time length. The first amount of time is different from the third amount of time, and the second amount of time is different from the fourth amount of time.