Capacitive Keystroke Reference Updating for Interference-Resistant Detection
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Solution Overview
Problem
Existing methods for updating keystroke references in fingerprint chips without a microcontroller unit (MCU) face issues of interchangeability, environmental interference, and weak anti-interference due to reliance on absolute thresholds, which are not adaptable to different fingerprint modules and environmental changes.
Innovation Solution
A method and module that dynamically update keystroke references by receiving pressing interrupts, obtaining multiple capacitance values, and setting release references based on these values, allowing for consistent operation across different keystroke chips and reducing environmental interference by updating references only after an interrupt occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an absolute threshold method is used to determine key pressing state, then the determination process is simple, but interchangeability between different fingerprint modules is poor
Solution Approach 1:
The patent changes the reference parameter from a fixed absolute value to a dynamic relative value. By calculating the difference between the current capacitance value and the reference capacitance value, and comparing this difference with a threshold, the system adapts to different fingerprint modules while maintaining a simple determination process. This resolves the contradiction by making the reference parameter adjustable rather than fixed.
2Ease of manufacture
If an absolute threshold method is used to determine key pressing state, then the implementation is straightforward, but the system is relatively affected by ambient temperature and external environment
Solution Approach 1:
The patent implements a feedback mechanism where the reference capacitance value is continuously updated based on the key loosening state. When the key is detected to be loosened, the current capacitance value becomes the new reference value for the next detection cycle. This feedback loop compensates for environmental changes by dynamically adjusting the baseline, thereby reducing the impact of temperature and external interference while keeping the implementation straightforward.
3Device complexity
If an absolute threshold method is used to determine key pressing state, then the detection logic is simple, but anti-interference capability is relatively weak
Solution Approach 1:
The patent transforms the detection approach by changing from absolute capacitance threshold comparison to differential comparison. By computing the difference between current and reference capacitance values, the system enhances anti-interference capability while maintaining relatively simple detection logic. The differential method naturally filters out common-mode interference signals.
4Adaptability or versatility
If reference values are updated continuously, then the system adapts well to environmental changes, but the main control chip bears extra burden
Solution Approach 1:
The patent employs periodic action by updating the reference value only at specific moments - when the key loosening event occurs. Instead of continuous updates, the reference is refreshed periodically based on detected key events. This reduces the computational burden on the main control chip while maintaining good environmental adaptation, as the reference is updated whenever conditions warrant a change.
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 enhances interchangeability and anti-interference capabilities by setting release references dynamically, ensuring consistency with the external environment and reducing resource burden on the main control chip, while maintaining accurate determination of pressing and release states.
Implementation Method 1
whether a fingerprint key is pressed or loosened is usually determined according to an absolute threshold... a key capacitance value changes as the finger presses
Data Source
AI summary
In keystroke recognition technologies, a method and a module for updating a keystroke reference, and a terminal device are provided. The method for updating a keystroke reference includes: receiving a pressing interrupt sent by a keystroke chip; obtaining a plurality of pressing capacitance values from the keystroke chip, where the plurality of pressing capacitance values include a capacitance value of the keystroke chip at a generation moment of the pressing interrupt and a capacitance value of the keystroke chip at a scanning moment next to the generation moment of the pressing interrupt; and setting a release reference of the keystroke chip according to the plurality of pressing capacitance values, to improve interchangeability and anti-interference of the keystroke chip with no extra burden on a main control chip.