Keyboard Circuit Scanning With Charge Cleaning for Accurate Key Detection
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Solution Overview
Problem
Existing keyboard scanning technologies are affected by parasitic effects in wires, leading to inaccuracies in key identification and increased complexity due to differences in key array design.
Innovation Solution
A method for scanning a keyboard circuit that includes a keyboard array with output and input wires, where each output wire is coupled to a column of key units and each input wire is coupled to a row with a pull-up resistor, and a scanning circuit that uses open-drain transistors to connect to ground for charge cleaning and independent scanning periods to determine pressed keys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wires are used to connect the scanning circuit and the key array, then the keyboard circuit can be assembled, but parasitic effects in the wires affect the accuracy of key identification
Solution Approach 1:
The patent extracts and removes the harmful parasitic capacitance effects from the scanning process by introducing a dedicated charge cleaning phase. During this phase, all open-drain transistors are turned on to discharge accumulated charges from the output wires, effectively separating the harmful charge accumulation from the useful scanning operation.
Solution Approach 2:
The patent applies preliminary action by performing charge cleaning before each scanning operation. The charge cleaning phase is executed in advance to remove parasitic charges from the output wires, ensuring that the subsequent scanning process starts with a clean electrical state, thereby improving measurement accuracy.
2Measurement precision
If a scanning circuit is used to identify pressed keys, then key position recognition is enabled, but charge accumulation from parasitic capacitance affects scanning results
Solution Approach 1:
The patent implements periodic action by alternating between charge cleaning phases and scanning phases in a regular cycle. During the charge cleaning phase, all open-drain transistors are activated to discharge parasitic charges. During the scanning phase, the transistors are deactivated for normal key detection. This periodic alternation ensures accurate scanning by regularly removing charge accumulation.
3Productivity
If the scanning circuit scans all columns simultaneously, then scanning speed is improved, but charge accumulation from parasitic capacitance cannot be effectively removed
Solution Approach 1:
The patent applies segmentation by dividing the scanning process into distinct temporal segments: a charge cleaning segment where all open-drain transistors are activated to remove parasitic charges, and a scanning segment where individual columns are scanned sequentially. This segmentation allows effective charge removal while maintaining scanning functionality.
4Adaptability or versatility
If different key array designs are accommodated, then adaptability is improved, but scanning complexity increases
Solution Approach 1:
The patent implements universality by designing a scanning circuit with open-drain transistors that can universally handle different key array configurations. The same basic scanning mechanism and charge cleaning procedure work across various keyboard layouts and designs, making the system adaptable without requiring complex configuration changes.
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 method effectively removes charge accumulation from parasitic capacitance, improving scanning accuracy and adaptability for different types of keyboards.
Implementation Method 1
prevent the accumulation of the charges caused by the parasitic capacitance from affecting the scanning result
Data Source
AI summary
A method for scanning a keyboard circuit is provided. The keyboard circuit includes a keyboard array, output wires, input wires, and a scanning circuit. Each of the output wires is electrically coupled to a corresponding column of key units of the keyboard array, respectively. Each of the input wires is electrically coupled to a corresponding row of key units of the keyboard array, and is provided with a pull-up resistor. The method includes: turning on and connecting open-drain transistors to the ground in a scanning interval to clean charges on the output wires; turning on the open-drain transistors and connecting the open-drain transistors to the ground sequentially in a scanning duration; and receiving detected electrical levels through the input wires, and when one of the detected electrical levels is substantially equal to the electrical level of the ground, determining that the corresponding key unit is pressed.