Smart Scanning for Capacitive Sense Arrays
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Solution Overview
Problem
Existing touch-sensor devices with limited receive channels face inefficiencies in scanning large capacitive sense arrays, leading to time-consuming and resource-intensive measurements.
Innovation Solution
Implementing a smart scanning method that logically divides the capacitive sense array into scan groups, using multiplexers to combine electrodes and perform a coarse scan to determine object location, followed by a fine scan for precise positioning, thereby reducing the number of necessary measurements and conserving resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential scanning of all sense elements is performed, then complete coverage of the capacitive sense array is achieved, but scanning time becomes prohibitively long
Solution Approach 1:
The capacitive sense array is divided into multiple scan groups, where each group contains a subset of sense elements. This segmentation allows the processing system to scan multiple groups in parallel using available receive channels, significantly reducing the total scanning time while maintaining complete coverage of all sense elements.
Solution Approach 2:
A coarse scan is performed first to quickly identify scan groups that contain conductive objects. This preliminary action filters out scan groups without objects, allowing subsequent fine scans to be concentrated only on relevant areas, thereby reducing overall scanning time while maintaining detection accuracy.
2Measurement precision
If all sense elements are scanned with equal detail, then detection accuracy is maintained, but power consumption increases
Solution Approach 1:
The coarse scan serves as a preliminary filtering step that identifies which scan groups contain conductive objects. By performing this low-power initial scan, the system可以避免 performing high-power fine scans on all scan groups, thereby significantly reducing overall power consumption while maintaining the ability to detect objects with high accuracy in the identified groups.
Solution Approach 2:
Instead of performing full-detail scans on all sense elements, the system applies partial scanning (coarse scan) to all groups and only performs excessive detailed scanning (fine scan) on the subset of groups that contain objects. This selective approach reduces total power consumption while maintaining detection accuracy where needed.
3Productivity
If the number of receive channels is increased, then more sense elements can be measured in parallel, but device complexity increases
Solution Approach 1:
The sense array is segmented into scan groups that match the available receive channel capacity. This segmentation allows the system to fully utilize the limited number of receive channels without requiring additional channels, maintaining measurement throughput efficiency while avoiding increased device complexity.
Solution Approach 2:
The system employs periodic coarse scans followed by selective fine scans on identified groups. This periodic scanning approach allows the limited receive channels to be reused efficiently across multiple scan cycles, achieving high measurement throughput without requiring a permanent increase in the number of physical receive channels.
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 allows for accurate detection and localization of conductive objects while significantly reducing scanning time and power consumption, especially in larger capacitive sense arrays.
Implementation Method 1
The capacitance detected by a capacitance sensor changes as a function of the proximity of a conductive object to the touch sensor
Implementation Method 2
using multiplexers to combine electrodes and perform a coarse scan
Data Source
AI summary
A method and apparatus scan a plurality of scan groups in a capacitive sense array to generate signals corresponding to a mutual capacitance between the electrodes. Each of the plurality of scan groups is formed from a subset of the plurality of electrodes. A processing device identifies a scan group where the generated signal is affected by a presence of a conductive object. The processing device individually scans the subset of the plurality of sense elements in the identified scan group to determine a location of the conductive object.